Well, as I mentioned to Keen earlier today in chat, for a very long time I thought we were restricted to two votes per question: either an up or down vote for 1) the question itself, and 2) the best answer, regardless of how many answers there were and if more than one answer was equally excellent. This obviously sounds like a huge FAIL, and it was -- but I truly didn't know you could vote on multiple answers to the same question. It hasn't been very long since I learned how to correctly vote. This is the main reason I have only cast 566 votes and I've been a member of SFF.se since November of 2011.
I mainly vote on Harry Potter questions and answers because they're the ones I feel most qualified to assess.
Sometimes I do vote on other kinds of questions if I understand the content well enough, for example Star Wars, Star Trek, SGA, Steampunk, and Lord of the Rings. If I don't know a question's source material well enough to determine whether or not the question is a good one, I'm not going to give it a vote, even if it appears excellent at face value.
I ask approximately as many questions as I answer; of course when asking a question you can't vote on your own question. So when I'm answering a question, I have to actively remind myself to vote on the question. I very rarely go back to a question once I'm done answering it, so sometimes I miss some really great answers from other users. This is something I'm working on improving, because I do want to be supportive of my fellow users, not indifferent toward them.