Thief is an immersive game, the more immersive you make it the better.

-Play with good headphones (2nd choice: a good surround system if you have it).
-Play in the evening with the lights out
-Play in 1-3 hour intervals or by mission, as the gameplay is excellent but
the stress can get tiring after a couple of hours.
-Minimize the chance of distractions
-Get the gamma setting right. Keep it as dark as possible while still bright enough that it doesn't impact gameplay.
-The graphics are dated, but you will notice less after an hour or so.
-Use quicksave instead of menu save to keep immersion, but never quickload unless the game crashes (rare) or you die.
-Don't play higher game difficulties on your first try. They are called "Hard" and "Impossible" for a reason. When ready, move up (you choose difficulty by mission).
-It can take a few hours to learn how to play well. It is worth the investment. A good suggestion if you're having trouble is to keep at the first post-training level until you finish it, then restart the game using what you've learned.
-Keep playing as long as Garrett lives. Every level is winnable no matter the setbacks, and the game is most immersive when you play through your mistakes.
-Flight before fight, learn it and apply
-Run->Hide->Wait->Try again
-Avoid killing, but don't be afraid to fight back if cornered (ie: don't reload, try to survive no matter what)
-(once comfortable) avoid blackjack

Thief is a very replayable game, the difficulty modes add a lot to gameplay, and even after you finish on impossible, you can still try ghosting (alert no one and leave no trace except for missing loot), extreme exploring, or speed runs. Since the game missions are so nonlinear, every play will be different if you allow it.

For an excellent 12-year long discussion forums on Thief, visit TTLG.com.

I like to try to blackjack everyone and pile their bodies up. The only levels I don't like are the ones with zombies! o_O Back in the day I used the level editor to remove them from the levels lol.

how do you quicksave? it's not in the shortcuts
-found it, reading the manual, it's F11 to quicksave, f12, quickload

Great post! I agree with everthing you said.

I've never played any other setting than impossible, just because it improved the atmosphere and immersion for me having more objectives, and more difficult guards.

Return to the Cathedral is the difficulty spike when playing on Impossible. There's some objectives that get revealed towards the end of the mission that you may not be prepared for and you can even get into the position of being unable to finish. So you'll have to load a save an play with the surprise objectives in mind.

In short, as well as using the quicksave key, make the odd 'hard' save too. When you complete objectives is usually a good time.

In some levels, you actually get additional content by choosing the harder levels. Keep this in mind if you choose an easy level so you can come back on a second play through.

And once you have master the highest difficulty level, try playing it Lytha style - http://www.ttlg.com/Forums/showthread.php?t=36890

Play in your room when your window is broken and it's -30 Celsius outside, really gives you the feel of a cold, dark night. Or a cellar. Or a tomb.

If you're experienced and have enough time on your hands, you can try playing with ghost or supreme ghost rules, thoroughly described here:
[url=]http://forums.eidosgames.com/showthread.php?t=30310[/url]

In fact, it's almost always the case that you cannot steal everything in the level (food included) while adhering to the supreme ghost rules. For me it's the ultimate challenge in Thief. Definitely not for the faint of heart or the impatient, but incredibly rewarding.

Bah! The ultimate immersion is to sneak into a friend's house while they're asleep and play it there without them knowing.

A friend's house? Bah! I only play super-secret-ultimate ghost rules. You have to break into a bank vault at night and play the game there without getting caught.

Hah! I thought I was the only one who did this sort of thing!