We should vote positively as often as possible! Also, we should encourage others to do the same!
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.
The rationale for wanting the base level to be high is:
- It provides better positive feedback to good contributors.
- This generates more reputation in the system, allowing more users to contribute in more ways as they gain privileges across the site.
- More reputation also means there is more rep to go around i.e. bounties. These are very good for the site in general, as bounties lead to the generation of even better content.
However, this does not mean that you simply upvote everything you see.