How do you upvote and acquire karma points at HN?

Thanks for the answers everyone. I spend so much time on this site, it's nice to be able to participate more fully.

Post interesting stuff, write constructive comments.

Interesting comment. How would I upvote it?

Click the little up triangle...

Ah, thanks. So that's the mechanism to upvote. So I guess the karma comes from participation and having comments and/or submissions upvoted?

Yes. Each time someone clicks on your little up triangle, whether a comment or a submission, you get +1 karma.

Users with a lot of karma also see "down" triangles and can downvote comments (though not submissions), so try and stay within the guidelines.

Say the opposite of what I would say.