My personal brand of humor is a mix of things: cynicism, hyperbole, satire, and sometimes gimmicky wordplay. If it's more lighthearted, I'll keep to good-natured teasing of character flaws. With the former, I usually square that humor up with characters that have a more serious nature, but whether or not they are the ones dishing it out or if I give their character a foil, or if I do it through third-person narration, I guess it all depends.
You can have a humorous character that isn't a total "goofball." Goofballs are not interesting to me. Often times I come across goofball characters and they are like an amalgamation of everything forced and groan-inducing. Likewise, you can have a serious character who still has a functioning frontal lobe, and can have a sense of humor, however dry or insulting. It's a balance we should find.
I do not use humor to make my character more interesting. That intent sounds more like a gimmick than anything, since writing humor usually has the goal of having the reader laugh with or at the jokes, so making humor such a high priority could compromise into attempted pandering to an invisible audience. I consider humor to be a minor trait in a character and is expressed as naturally as I would express mine--because the only humor we as writers know how to execute best is our own.