Dude, patience is a virtue. There is no rock solid set in stone answer. If we had it, we wouldn't be here!
You need to get links to your site, links to your main forum, links to the forum category your posts are in, links to the forum in question, and links to the thread.
Links with anchor text related to the post you are wanting to rank will definitely help. The number of replies and recent history of the thread also has some affect I believe nowadays with the Caffiene update google has done.
