Personally, I set up my keyboard for single-player, since I usually don't have anyone to play with.
WASD is for movement, obviously.
For attacks, I have it set as the following on the numpad:
(A = 4) (B = 5) (C = 6)
(X = 1) (Y = 2) (Z = 3)
It's nice and comfortable to use, and the buttons aren't weirdly positioned.