Posting comments - like this one - I believe that is the easier one.
If you have several machines capable of running metatester - leave them on.
Vote on polls.
Reply to comments.
You'll see that some categories seem to have very low max points, probably cause its so easy to get points therein.
You missed one item: report bugs to helpdesk.
I think that the best way to accumulate rating points quickly is to create new branches of the forum.