As a regular user of Wikipedia, I figure it's only fair that I contribute as well. This tends to happen in bursts -- I did a lot of editing in early 2008, had another burst of activity in 2009, got lazy for a while, and am getting involved again as of 2014.
I work as a journalist and editor in Australia, so my corrections have tended to either involve fixing grammar, expression and structure problems, adding some global perspective and information to US-centric articles, tweaking around the edges of pop culture-related articles, helping remove blatantly non-encyclopedic content when it sneaks in, or adding sources to existing articles and improving the formatting of sources already present.
I often perform good-faith edits: assuming that information in a given article is accurate (even if there are no references), and editing the material so it more closely matches Wikipedia guidelines for expression, article structure and neutrality. On topics that attract dedicated fans, this can sometimes be a riskier enterprise than it sounds -- people can get very offended even if you're removing obviously inappropriate material and have gone to pains to explain your reasoning on the talk page. My hide is getting thicker as a result.
I'm firmly of the belief that articles need references to be of any use, but recognise that many enthusiasts don't understand reliable sources policy or find reference tagging confusing, so I always try and presume information is accurate and help add references rather than just removing stuff, unless it's self-evidently inappropriate.