It depends on the game, really. For MMO's I'll min-max right up to just after character creation, because I'll be damned if I'm going to pick a race for its 1% bonus to whatever over a race/class combo that I actually like. Plus, for games like WoW, leveling in min-max mode can actually be pretty challenging if you're playing a class you know. But any time my worth as a human being is decided by 5 minutes of generating random numbers, I'll pick the build and gear that makes the highest numbers appear most of the time.
For co-op games, it's what I like and what my friends need at the time. If I roll a mage, but we're eating damage pies because no one is tanking or supporting, I'll forego amazing dps for support, and switch to a more useful class if necessary or practical.
For single player games, especially Skyrim, I usually take skills I think my character would want (but not skills that are completely useless, like about half the skills in Might and Magic VIII). I've broken my own darned immersion in Skyrim before by trying to make a character who is good at everything.
For D&D, I'm trying to DM, and find it's much easier to use pre-made monsters than make my own xD. But then again, I'm playing 4ed, which is evil and horrible, but much easier to learn for a group of people who honestly don't know much about D&D...
