I belive we shold follow the advice of Scott Morrison: vote early, vote often. This is a way to express which questions are on- or off-topic, and the site needs high rep users.
It's worth explicitly stating why we should vote early and vote often - upvote the stuff with merit; downvote the bad stuff. Both questions and answers. I've copied the material from abatkai's link, below, for ease of reference.
Every Stack Exchange site will eventually end up with a different "base level" of voting --- that is, the expected number of upvotes for a question of a given level of excellence. (This effect occurs because people see a good question, but already with a certain number of votes, and think "oh, I would have upvoted this, but it already has enough".)
It's easy for us to affect this "base level" by encouraging high levels of upvoting now. We're setting the standards, and this really will have an effect.
(On MathOverflow, we were very active about this early on, specifically encouraging all the initial round of users to vote early and often. You can compare statistics, and see that the average vote total for a MathOverflow question is much higher than on any of the other SE 1.0 sites.)
In case it's not obvious: the rationale for wanting this base level to be high is that it provides better positive feedback to good contributors.
A good rule of thumb: if you can be bother answering the question, it's good enough to upvote! Also, be kind, and upvote any good competing answers that exist when you give your answer.