People who have more then 10 posts can give + karma, or - karma.
Only one point every hour to each person.
Admins don't have such a limitation.
If you really like someone's post or info/idea give him a +1. If you think that person made a very bad and terrible post with very miss-leading info or very rude messages, then you might consider giving him a -1.
As you start to make more good posts people will give you more and more karma.