Something that I have found relatively strange on this site is that sometimes questions receive a good response, yet they have no upvotes at all. For instance, I read a good question today that had two valid responses. The question and both posts had no upvotes. The interesting thing to me was the fact that the two users who responded found the question interesting/good enough to answer, but not good enough to upvote? I don't understand that.
We should be upvoting as often as possible. It promotes a stronger community and it provides incentive for users to provide better questions and better answers. Now, they may just be fake points and I doubt anyone's goal here is to really just get the highest score, but it is a good mechanic that this particular site doesn't utilize enough in my opinion.
The way I view it, if the person takes the time to write a question, as long as it looks like they put some time or effort into it, it should get an upvote. Even if it is something I already know, it is something that clearly others may be looking for at some point. If it is formatted well and provides a clear logical question, give it an upvote! As Daniel pointed out, upvotes are free. Let the users know this is a site where we appreciate questions, small or large!