This is a compiled list of tips, tricks & tweaks for Windows Vista, using this 3 year-old thread started by Martin L as a base.
For each entry copied, the original poster has been credited.

Where possible, the tips have been verified as accurate on Windows Vista x86 SP2 (running under Hyper-V on Windows Server 2008 R2).
Some of the original entries were only applicable during early betas and so have not been included.
Each entry is tagged as [verified] if I managed to implement it can confirm the desired effect.

Where external references were broken due to age, they have been removed.

Tips fall into 3 categories:
- through the UI with user interaction
- through group/local policy editing
- through registry editing

The UI methods are often just a friendly front-end for editing the registry, and group or local policy is just a set of dynamic changes to the registry without "tattooing" it (so they are reverted back to their original settings if you return to "not configured") - so there may be multiple ways to achieve the same goal.

At the end is a discussion on a few common "performance tweaks", with citations from the original thread where available, along with my personal views & reasons for not using any of them.
The section is thus named "tips of contention" - I can guarantee there will be people that disagree with me and will claim first-hand experience to the contrary.


To add to these posts, please PM me the addition or a pointer to an existing post to copy/paste from.
To keep the thread clean it has been locked, questions can be made in separate posts if needed.

GENERAL TWEAKS & TIPS

FthrJACK
Enable file extensions in Explorer [verified]
From an Explorer window, click Organize / Folder and Search Options
Select the View tab
Untick "Hide Extensions of Known File Types" and click OK

gunsmokingman
Change the size of the icons on the desktop [verified]
Note: Also cycles through the view types in Explorer, and scales pages rendered in Internet Explorer
Hold down CTRL and use the mouse scroll wheel

nitropuppy
Using Flip3D feature (on systems running Aero Glass) [verified]
Open a few windows then press the Win key + TAB, this makes them all visible each behind the other
(Hitting TAB whilst holding down the Win key will flip between the open windows)

xper
Open a command prompt window from any folder [verified]
Hold down SHIFT and right-click the folder in Explorer - click the new context menu option "Open Command Window Here"

"Run" command Start Menu option (one-off) [verified]
Hold down Win key and press R

"Run" command Start Menu option (permanent) [verified]
1. Right-click on the Start menu and choose Properties
2. Click on the Customize button
3. Check the "Run command" option, click OK, click OK

ElAguila
Enabling / disabling User Account Control (UAC) [verified]
Control Panel > User Accounts and Family Safety > User Accounts > Turn User Account Control On or Off

Spooky
Disable hibernation (remove hiberfil.sys) [verified]
Open an elevated command prompt and enter the command:
powercfg -h off

Windows Internet Computer Names [verified, pointer to TechNet article]
"Have you ever wanted to be able to find and connect to your home computer across the Internet, but did not want the complexity and cost of buying a domain name and managing Domain Name System (DNS) records? With Microsoft® Windows Vista™, you can use Windows Internet Computer Names.
This article will show you how to configure a Windows Internet Computer Name and use it in common tools and applications."

Increasing hard disk performance [verified, but be sure to read the on-screen notes]
Go to Control Panel > System and Maintenance > Device Manager
Expand Disk Drives
For each drive, double-click it and select the Policies tab: make sure "Optimize for Performance" is selected, and if available also tick the "Enable Write Caching on the disk" and "Enable Advanced Performance"options, click OK

Enable update of "Last Accessed" on files [verified]
Note: This can have an impact on disk performance, as opening a file for reading will now incur a disk write to touch the file
Open an elevated command prompt and enter the command:
fsutil behavior set disablelastaccess 0

Prevent USB hubs turning off to save power after idling [not verified]
Note: USB devices (typically hard disks) that were told not to turn off were found to have issues if the hubs were considered idle and being disabled
Go to Control Panel > System and Maintenance > Device Manager
Expand Universal Serial Bus Controllers
For each item 'USB Root Hub', double-click it and select the 'Power Management' tab: uncheck the box 'Allow the computer to turn off this device to save power', click OK

Keyboard shortcut for Task Manager [verified]
CTRL+SHIFT+ESC

Assigning keyboard shortcuts to programs [verified]
1. Create a shortcut for the program, then right-click it and select Properties
2. Select Shortcut tab then click inthe 'Shortcut key' box
4. Press the key that you want to use for your shortcut, then click OK
Note: The keyboard shortcut you are creating is triggered with CTRL+ALT held down
Note: If you accidentically delete the shortcut (.lnk) file, you will need to unassign the shortcut key and then re-assign it again

Avoiding 'Open File - Security Warning' popup for downloaded files [verified]
Files downloaded from an untrusted location, such as the Internet, are automatically tagged through "Internet Security Zones", and attempting to such run a program will present a warning dialog box asking "Do you want to run this file?"
To prevent seeing this message, on the General tab of the properties of the file, click the Unblock button
Alternatively, on first run, untick the box "Always ask before opening this file"

Make a program shortcut always run elevated [verified]
On the properties of the shortcut, select the Shortcut tab and click the Advanced button - check the box "Run as administrator" and click OK twice

Automatically log on [verified]
Note: The user account to automatically log on as must already exist, and this is definitely not recommended for Administrator accounts
Click the Start button, enter in the Search or Run box: netplwiz
Uncheck the box "Users must enter a username and password to use this computer' box, click Apply
Enter the name and password (if any) in the fields presented, click OK on both windows

Custom toolbars on the desktop [verified]
Create a new folder on your desktop and populate it with your shortcuts/files
Drag the folder to the edge of the screen and let go of the mouse button
Note: You will still have the desktop icon for the folder, and you shouldn't delete it, you can however relocate and resize it to suit

mcarfixer
Address toolbar at the top of the screen [verified]
Using the trick above to create a toolbar at the top of the screen, right-click the toobar and from the Toolbars context menu add the Address toolbar
Right-click on the original toolbar and click "Close toolbar", you can now delete the folder from the desktop (it has served its purpose)

fizban2
Launch an application elevated from the Start / Search box [verified]
Click the Start orb, in the Search box enter the name of the application, then hit CTRL+SHIFT+ENTER to request elevated launch

Mr Snrub
Recovering a Recycle Bin accidentally deleted from the desktop [verified]
Right click on the desktop, click Personalize
Click 'Change desktop icons'
Check the box 'Recycle Bin', click OK

POLICY TWEAKS

Tripredacus
Disable password requirement when resuming from sleep [verified]
Computer Configuration / Administrative Templates / System / Power Management / Sleep Settings
> Require a Password When a Computer Wakes (On Battery) : disable
> Require a Password When a Computer Wakes (Plugged In) : disable

Disable Link Layer Topology Discovery [verified]
Note: Can reduce delays accessing shares on legacy Windows machine, but also disables the Network Map feature
Computer Configuration / Administrative Templates / Network / Link Layer Topology Discovery
> Turn on Mapper I/O (LLTDIO) Driver : disable
> Turn on Responder (RSPNDR) Driver : disable

Spooky
Disable Media Player's automatic updates [not verified]
Computer Configuration / Administrative Templates / Windows Components / Windows Media Player
> Prevent Automatic Updates : enable

spacesurfer
Disable web services for unknown file types [verified]
Computer Configuration / Administrative Templates / System / Internet Communication Management / Internet Communication settings
> Turn off Internet File Association service : enable

REGISTRY TWEAKS

Spooky
Add "Open Command Prompt Here" option to context menu [verified]


Remove arrows from shortcuts [verified]
Note: This is a better method than removing the "IsShortcut" registry value, which breaks links in Games, Favorites, Media Center, etc.


Disable UAC [verified]


Enable UAC [verified]


Prevent "- Shortcut" being appended to new shortcut names [verified]


Disable splash screen when launching Windows Mail [verified]


Turn off UAC consent prompts, but leave it enabled - admin users [verified]
Note: This makes members of the Administrators behave the same way as the built-in Administrator account


Turn off UAC consent prompts, but leave it enabled - regular users [verified]
Note: This removes "over-the-shoulder" (OTS) prompts, so users are unable to request elevation, and get access denied for all administrative tasks


Disable "Hide operating system files" in Explorer [verified]


Disable tooltips [verified]


Allow >2 simultaneous downloads per server through Internet Explorer [not verified]
Note: RFC2068 dictates that clients should be limited to 2 simultaneous persistent connections per user, and Windows/IE adheres to this by default but can be overridden (below are the default values, you will need to edit them to suit)


Disable Media Player's automatic updates [not verified]


spacesurfer
Remove the "Delete" option from the context menu of the Recycle Bin, to prevent accidental deletion [verified]


Replace "Computer" with "%username% on %computername%" [verified]
Note: Does not change the Start menu "Computer" link, but the desktop and breadcrumb trail objects are modified


Add "Advanced System Properties" to Computer context menu [verified]


wiSHmaKeR
Enable underlining of 'active' character in menu items (i.e. ALT key combination to select that item) [verified]


arabianhorse
Disable "low disk space" warnings [not verified]


spacesurfer
Disable web services for unknown file types [verified]


TranceEnergy
Maximize worker threads on heavily loaded systems [verified]


Prevent kernel and driver code from being paged to disk when not in use [verified]


Lance_315
Enable Windows Aero in Vista Home Basic [not verified]


alrichdesa
Add "Copy To Folder" to Explorer context menu [verified]


Add "Move To Folder" to Explorer context menu [verified]

TIPS OF CONTENTION

Some tweaks & recommendations are based on previous versions of Windows, experience during beta testing rather than RTM, experience from specific hardware configurations, or simply "I heard this somewhere so it must be true".

The most obvious ones I can think of are:
- Disable the Superfetch service [to reduce disk I/O]
- Enable LargeSystemCache [to increase the maximum size of the system cache, as used by file servers]
- Disable the Windows Search service [to reduce disk I/O]
- Turn off the page file completely [to reduce disk I/O and make the system more responsive]
- Disable services X, Y and Z [to recover wasted system resources]
- Hack TCPIP.SYS to allow more than 10 simultaneous outbound connections


SUPERFETCH




On the following remark I have to call foul on technical accuracy (not opinion):
"The obvious disadvantage is anything else you do during this precaching will be slower in addition your hard drive is been stressed"
Superfetch and Windows Search have low priority threads and I/O - if you request something of Windows and it is currently using slack time to do either of these tasks, then they are paused and yours takes precedence.

The effectiveness of Superfetch will depend on how predictable your usage is, but I believe it hits way more than it misses, and every cache hit saves you a disk I/O - which might potentially interrupt what you were currently doing, giving you a poorer experience.
As it builds up a usage pattern over time, and makes its decisions based on logged-on user and time of day, its accuracy gets better as time passes.


LARGESYSTEMCACHE

This is an old tweak for XP, which used to cap the amount of memory used for the system cache quite low - setting the above value to 1 would allow the system cache to expand and use a lot more memory, which is the default for Windows Server 2003.
Superfetch is (pre)populating the system cache with file sections (not entire files necessarily) and Vista users quickly noticed that "Free" memory appeared to disappear after booting up, scaring them into believing they had some kind of memory leak - this is the indication that the system cache is already "large", and the registry setting doesn't really do anything.


WINDOWS SEARCH
Similar to the Superfetch argument, the Windows Search service provides a more positive than negative experience for the majority of users.
First, it is not "constantly indexing the data" - content is indexed once (which may be a long operation on the first pass, just after install), then only again if it is modified.
The more files you have of various types, scattered over many locations, the more benefit you get from an index.
Content from various file types can be indexed (including inside email programs) for quick location - much faster than a trawl of the contents of every file on demand.
An argument is often "I am organized and put my files where I know how to find them", which is fine - except do you file a photograph of your parents on holiday in 1996 under "Family", "Vacations", "1996"?


PAGEFILE
Turning off the page file (or at best, fixing its size to "prevent fragmentation") - this is one I've never seen any statistical data to back up the claim that this helps at all.
Windows works on a virtual memory model, the sum of physical RAM and some space on disk - the former being a limited and more valuable resource, so when it contains data or code that has not been used in some time, it pages it out to disk to make the space available for something that might make better use of it.
The theory is that not having page file forces everything to remain in memory (which is mostly true) and thus makes programs and data "instantly" accessible.
The major drawbacks with this:
- some applications will flatly refuse to start without a page file
- if Windows bugchecks then it is unable to dump the contents of memory to the disk for analysis
- more physical RAM used means less space for the system cache, so potentially more disk I/O


SERVICES
Disabling services has long been held as a performance tweak for Windows - some people claiming to know exactly what each service does and why you don't need it, and that turning it off will greatly improve your life.
A lot of services are used by the OS internally, and those that don't need to run all the time are set to do start on demand and stop after a few minutes of idle time.
A service that is running but isn't been asked to do anything consumes 0 CPU cycles, and if it has not been doing anything its virtual address space contents will be paged to disk, so it isn't wasting any measurable amount of RAM.
A service that isn't needed will incur disk I/O and CPU time only when it starts up.
There is a school of thought that says an uneeded service is a potential security hole, but this is generally only true if the service has a listening port that is not firewalled and requires authentication - logging on as a non-Administrator user is the best mitigation for exploits to services, and Windows Vista implements more levels of privileges for service accounts (e.g. a service that only accesses local files does not need any privilege to access the network).


TCPIP.SYS
The hack (be it a replacement file on disk or an in-memory patch) to modify the number of half-open outbound TCP connections is no longer applicable as of Service Pack 2.
It was commonly misquoted that the introduction of the limitaiton in XP SP2 meant no more then 10 connections could be established from the client at any given time, the reality is that at any point in time there could only be up to 10 being set up (hence half open) - once they were completed or rejected they did not count towards the total.
The intention was to reduce the impact of clients infected by malware being able to spread to other machines, which it did - the only applications that were negatively affected were of poor design that would attempt to establish multiple TCP connections without verifying first if the endpoint is accessible (i.e. not firewalled or behind NAT), which meant "torrent" applications mainly.
It did not, however, affect the speed of the downloads once the client had got past the initial search for seeders.
It is no longer applicable as the restriction was removed in SP2, so there is now nothing to hack/patch.


HYBRID SLEEP
Taking all the above into consideration, now it should be apparent as to why using hybrid sleep & waking the computer is preferable to shutting down & starting up:
- services don't need to start, so no disk I/O or initialization routines to wait through
- system cache is already populated, so no disk I/O
- "button to desktop" time of ~2 seconds, and the system is ready to go (compared with a POST, startup time, profile load and prefetching with a cold boot)