[raxxorrax]

It really depends on the topic as well. In the vast majority of cases people are reluctant to dish out any karma and your comment stays at one point. But that changes for some topics. I guess if you want to get more upvotes, articles about new Apple releases and similar stuff is most rewarding.

[noduerme]

It doesn't decrease your karma to upvote on this site, although that might not be the worst idea.

Come to think of it, I'm not sure why other people are so stingy with upvotes. I vote pretty much everything I like.

[verdverm]

The best is to comment early on a front page story, not necessarily a top-level, but if you land within a few folds of the top, more eyes more votes.