Well, multi is fun, going with fighter/thief, and most races are good with elf being nice in that you can get some killer dex (up to 19) and str, but loose out on some con (limited to 17), or the half-orc is pretty brutal too.
Disadvantages are that you only get 2 points in weapon profiency, and can only backstab with backstabable weapons (Scimitar/Wakizashi/Ninja-To, longsword, shortsword, katana, club, and quater-staff, but that is for any thief anyway), you do get better THAC0 and more hitpoints. You can wear more armour but you will loose your thiefin abilities if you do.
Duel-classin' is what I did. Get your human fighter up to 9, then duel class to thief, you need to have 17 or 18 dex in primary stats of fighter and thief to be able to do this. Advanatages: weapon profiency up to 5 like a fighter
more hit points.
Even though some don't like to use shadow keeper it is nice because I like to use the thief style character (the default for duel class fighter/thief is the fighter and you can't change that), and it allows you to assign the weapon proficency the right way, instead of forcing you to spend it when you wanted to save it.
A lot of the board members love the idea of the kensi/thief (duel-class) as you will get some awesome backstabs.
Straight thief can be done, and some of the more rewarding are assasin and bounty hunter. Either one is nice to play, especially if your into the rogue live style.
Good luck
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Drink and be merry
Jimbo
"Renegade, Rebel, and Rogue"