I always think "Would I be happy about this if I were on the receiving end". If not, I think harder and find other reasons to do bad things
Oh ok THIS IS SRS THRED?
then next I consider whether my actions benefit more than they piss off.
If the answer is still no, then morally it's a bad thing. But occassionally I play the family joker card -yes I would hate it, yes it's pisses off more than it benefits, but.... my daughter will die without a heart transplant so it's OK to murder this 10yo girl I found in the park. Just as long as I do it quickly enough that the heart will be harvestable.....
(that example may have been a little extreme, but you get the picture...)