• Use the shadows, make some by dousing torches but there is no need to put all of them out, it's a waste of water arrows.
• Crouching really does help in making you less visible in some places.
• Use your lean keys to check corners rather than blundering into a guard.
• Use your creep key to be even more stealthy, though you will also move slower.
• Reclaim unused arrows. Many broadheads, noisemakers, and all rope arrows can be reclaimed for later use. Simply look at the arrow until you can get it highlighted then pick it up.
• If your visibility crystal is bright enough that you have a yellow status you are at risk, many guards will not notice you but if alerted you're hosed.
• When your visibility crystal is dark enough that the status is black (neither yellow or red) not only are you invisible, but even an alerted guard will have problems finding you. If the surface is soft enough, you can even walk around the guard as he/she/it searches for you without detection.
• Use your drop key. Sometimes your inventory can become cluttered with unneeded objects, drop 'em or if you're worried you need them later, drop them and pull up you map and make a note of the location by clicking on it and typing in a message.

• Guards generally patrol hallways and don't stray into the rooms, hide in these rooms until the guard(s) have passed you.
• If you must fight a guard (which you shouldn't be doing anyway), Bigfishrobber suggests you keep moving to the opposite side of the guard's sword hand. Keep using the right slash with a little mouse twitch to face the guard. Since they can't turn as quickly you get the advantage.
• If you have to fight several guards (which is a bad idea) IceSyckel recommends using a doorway as cover. With room for only one guard to pass it will block the others while you are fighting.
• If you must risk exposure, make it quick by running and do it when you have the most distance between you and the guard.
• After opening a door, closing it helps. Guards can't see through solid doors though doors with glass panes won't help closed or open. This also cuts down on the noises you make being passed along into other rooms.
• If you have alerted a guard try running away closing doors behind you, sometimes it works.
• Guard still in pursuit? Try changing your height relative to the guard. Though jumping atop a table doesn't always work, climbing a ladder and diving into water usually does.
• When running away doesn't work throw out a flashbomb and blackjack the sucker. Don't worry if you're blinded, Garrett usually recovers before the guard does, more so if you manage to look away before the flashbomb detonates.
• If more than one guard is in pursuit, you better be close to the end of the mission as these things tend to end in reloading a game save.
• The small chattering gold children are blind, they can only hear or touch you for detection.
• Ibn Shaun has suggested a strategy invol.... we'll I'll just let him explain it:

  The Blue children of Karras have a built in "defect". Their left cannon arm is laterally spaced approximately one foot away from their eye. Because of this, while their real eye may have line of sight to you, their cannon arm may not. However, their decision to fire is based only on what their eyes see. This strategy exploits this to get the blue children to kill themselves:

  • Have the child follow you to an entryway, column, or other structure such that the child's cannon arm is hidden from your view.
    
    

  • Child
    -----+
       |
    -----+
     You

  • Keep moving back into and out of sight until the child is right up against their side of the wall. At that time, stay in view. (It helps to keep your fire arrows equipped, so that you are always visible. If they rely on "audiotory indications" only at that range, it usually results in a reload of the save game.)
  • The child will fire their weapon .. the cannon ball will hit and explode on them. The child usually steps back after taking the hit.
  • Move back out of sight, let the child get close to the wall again, and move back into sight.
  • Often, only two hits/explosions will kill them.

• Some narrow passages are difficult to get into even when crouching. This is were leaning forward can help. Check your key bindings for details. (Default: Ctrl-Alt-W)
• Having problems reaching a switch? If its of the push button variety a broadhead arrow can be used to trigger it.
• Want that door demolished? Wooden doors can be blown open by throwing a mine at their base and then detonating them with a broadhead arrow.
• Beware panes of glass, they give you the illusion of protection when you can't hear what is behind it, but any guard or mechanism can see you as easily through glass as if you were in the same room.
• Avoid jumping onto a surface its very noisy. Exceptions to this are carpet, moss arrow covered areas, and some outdoor terrain. In fact, it can be safer to jump from one carpeted area to another rather than trying to cross the marble floor between them.
• Wished you had a piece of paper to write something on? You already do, pull up the map and flip the pages until you find the notes section. Click anywhere on the page and type away.
• If you throw forgbeast eggs at an enemy and it dies, techincally its death by frogbeast not by Garrett and thus will not fail your mission should there be a "no killing" objective.
• Detonating large explosives, such as the suburst, can be done by either shooting it with fire arrows, or even by just throwing a lit flare at it. (Thanks MrchHare)
• Many wooden doors can be bashed open using your sword. (Thanks Ford)
• If the remains of a child of Karras blocks your passage, repeated bashings with either your sword or blackjack will eventually break it into smaller pieces. (Thanks hemlock)

   If you must there are few available:

• Pressing Ctrl-Alt-Shift-End will terminate a mission in success.

Thief 2:

• Open up the user.cfg file found in the root of the Thief 2 game directory. Uncomment (remove the semi-colon) the cash_bonus line to give yourself more loot at the start of each mission. Set the number to whatever you want to start with, the default value is 1000.
• Also in the user.cfg, uncomment (remove the semi-colon) one of the starting_mission lines and save the file. After Thief 2 has loaded start a new game. Instead of beginning with mission #1 you'll begin with the mission you uncommented.
• Add this line to the user.cfg file: cheats_active. After it on a separate line add either lockcheat or nokillgoalcheat, or both. Lockcheat will make any locked door unlocked when the mission starts. The NoKillGoalCheat disables the "Don't Kill Anyone" or "Don't Kill the Innocent" mission objective should one be present.
• Anti-Cheats can also be added to the user.cfg file. FailOnSee, FailOnKO, FailOnKill are fairly easy to understand and will add considerably amount of challenge to Thief 2 even on the normal setting! Just add one or all on a separate lines after you have added cheats_active.

Thief: Gold + Thief: The Dark Project:

• Money cheat: You can give yourself loot by adding the line cash_bonus to your dark.cfg. If set to an integer, its value is added to your loot total for loadout purposes.
  

  With 'cash_bonus 3000' added to your dark.cfg file, go into the game. When you get to the "Loadout" screen, immediately hit ESC, then SAVE. LOAD the game you just saved. You'll return to the Loadout screen, and another 3000 gold will be added to your purse.

  Repeat until you have as much gold as you want/need!

• Starting Mission - You can start the game at a mission other than Lord Bafford's Manor by putting the line starting_mission X in your dark.cfg. where X is the mission number to start at. When you select New Game, you will start at that mission. Note that although Thief: The Dark Project follows a sensible order the extra missions Thief: Gold has are actually missions 15,16 and 17. Entering 18 will get you the Blooper mission.

Thief 2 Patch (v1.07 to v1.18)	The Thief 2 patch. A must have if you want to truly enjoy the game the way it was meant to be.
Thief 2 Patch (for the SoldOut edition)	The "other" Thief 2 patch. Download this one if you purchased the "SoldOut" edition of Thief 2. The original patch will lock you out of the game.
Lytha.com	What Lytha likes to play gets documented here. Loot lists and walkthrough for Thief: Gold can be found here along with some stuff on Thief 2. Official site for the Lytha style method of playing Thief.
Keepers' Chapel	Walkthrough and loot lists for Thief 2 and Thief: Gold. Hey, it never hurts to have a second opinion. Also, I doubt I'll ever do a loot list, trying to track all that stuff is maddening. :-)