When I create a character, I never explicitly state whether he/she shall be good or evil or anything in between. Rather, I give them a personality which will affect their actions and shape their beliefs as they wander the wastes.
For instance, considering the nature of my latest character and the situation he's in, his karma has sunk to 'Very Evil'. Read the 'hardcoe' thread to catch up on some of his recent endeavours.
Arguably, the personality of the character itself could have clear good/evil connotations attached, but I still believe it's more flexible than simply deciding the character's morale alignment right off the bat, and then desperately trying to uphold it throughout the game.
EDIT: That said, I voted 'Evil'. Like I said, it's not necessarily what my characters strive for, though a fair few have taken that route. Perhaps it's a reflection of me? I find playing as a saint boring, for the most part, so instinctively instil certain undesirable traits within my characters.
However, as it happens, my first two characters both ended with 'Very Good' karma.