I'm generally good in games just because playing an evil character often means being a homicidal maniac and ends up with you being hated by everyone.
My preference is to play similar to what I'm like in real life - I'm definitely good natured but I'm also not moronically heroic as many games seem to push you towards, I try to make the safest bet even it involves unfortunate losses and sacrifices.
When I play "evil", if the game is flexible enough to play the kind of evil I like, I play as more of a neutral evil -
typically selfish and have no qualms about turning on their allies-of-the-moment. They have no compunctions about harming others to get what they want, but neither will they go out of their way to cause carnage or mayhem when they see no direct benefit to it. They abide by laws for only as long as it is convenient for them.
neither bound by any sort of honor or tradition nor disorganized and pointlessly violent.
in DnD terms.