Hmmmm, since you're not an author(like me last year xD), I think you can gain karma points by creating a blog, commenting on other users story, I think so get a reply, hmm.. When someone posy a message on your wall...
I think soo... Hope this helps ^^

commenting gives you karma if you aren't an author

From AFF FAQ:

Q: Why isn't my karma going up? How do I increase it?

A: You can increase your karma by
Commenting on a story (not your own)
Commenting on a blog (not your own)
When a story you wrote gains a new subscriber
When a story you wrote gains a vote

To curb behavior that goes against the spirit of why the karma system was instituted, karma will now only increase if the comments made are on different stories within a 24 hour timeframe. When 24 hours have passed since first commenting on a story, comment karma can be gained from the same stories once again.

For example, to gain 10 points, you'll need to comment on 10 different stories in the same 24 hour time period. After 24 hours, you can comment on those stories again for karma. Maximum limits are also in place in 24 hour time intervals. The same restrictions are in place for blogs.

If you comment on stories you can get some karma points (: I got all mine from subscribers and stories, so that's how mine accumulated. Only thing is, I have no idea what karma points are for >.<

i think it works when you get subs && comments on your stories & as you as an author...but i'm stupid when it comes down to aff too so x.x