The rivets are earned by the number of posts you put up. This is a little incentive to keep as many people as we can involved and participating. We have a number of members who read posts, but don't add any info, or ask any questions. We encourage everyone to ask away!
Karma is earned for you by the people who read your posts, and hit the karma button at the bottom to say that they agree, and like the post, or to make comments regarding it.
The more karma you have the better accepted the posts. This part is quite optional.
If you have any suggestions feel free to submit them. We are rapidly growing as a community on the web.