There are things you need to know, things you must adhere by...... of course you don't have too but its your business and you want to carry your self and your brand in the best possible light.
1) Take Time to READ the rules, its not your site and how would you feel if some one was misbehaving on your site most don't mind you linking relevant helping posts.
2) Stated in number one if you post in a thread make it relevant make it helpful you want that person coming away from your site with a positive experience these people have friends that may too have the same problem and also have the ability to slate your link to the whole community.
3) Yes the idea is to get sales but that doesn't mean you should be selling the theme here is to help them your post if the content is good will do the selling say something like "hey I see no one as answered you yet why dont you try this link it may just answer your question"
4) Don't spam no one likes spam and don't be afraid to even link to another site if you don't have the answer this will build trust and credibility
5) Expect your bounce rate to go up, personally I don't care to much for bounce rate, as far as I know neither do google, remember this is super targeted there more than likely interested in that post and that post only.
6) Follow up, don't be scared of feedback ask if they found what they was looking for if they didn't then think about adding the information for the next visit this will help with ranking
These are the 6 rules I am going to follow and there probably is more going forward!!
Hope you liked this tutorial please leave a comment and like and share for every one to benefit
Steven