There are
numerous places which discuss this. Go read.
Bear in mind that so called "fluff" posts in the Marketplace forum are not allowed; they will be deleted, and may well result a premature severance of your posting ability. Posting very short posts simply to increase your post total is frowned upon. And no matter how many posts you make in forums which do count towards the post total, you won't be able to start a Marketplace topic until you've been here for at least two whole days.