I generally don't vote for any candidate that hews too closely to the party line. I prefer candidates who think for themselves instead of mindlessly spouting the party position when asked a question.
It depends really. If there is no sure winner, or one canidate who I dislike intensely leading the polls, I will vote for a canidate who I believe to be the closest to my veiws on things. If, however, there is a tight race and I know it is going to be one of two people, I vote for the lesser of two evils. I figure, whichever way works best to get the most issues I care about raised and voted on.