I believe that the points are based on the quality and length of your thread or post.  Better quality means more points.  And I think that the more people that post in your thread, the more points you get. 

That is what I think is right anyways.  Someone please correct it if its wrong.

I don't know the exact formula (Satanta clued me in when he was about) but it's like what Hayley has said. The better your own posts, regarding content and length, the more points you will get.

If you start a post/thread then I believe the better quality the first post you start the thread with, the more points you will then also get from following replies (I think this is what he said). Also, the better quality replies your thread gets, the more points you get, but only in comparison to the quality of the post you started the thread with.

Now, if anyone could also correct me if I'm remembering it a little wayward much appreciated.