Mostly I just browse wiki looking for little errors to fix. Typos, links, grammar, etc.
I'd love to make larger edits, and actually add content, but most subjects I'm familiar with either have plenty of information, or I don't have sources for.
So most of what I do is just make things look tidier until someone else can come along and add more info. Or just make things tidier in general. I guess I'm a wikignome.