Engage the community. Give them a reason to want to interact. Seed the forum with questions that are just begging to be replied to. Get your friends to post and get discussions -- and debates! -- going amongst you.
First of all try to contribute to the forum, quality forum posting and you should have a clear goal and you should have good knowledge about the subject that you are discussing in forum would help you a lot.
There are few things which give an attraction to peoples for posting in forums. anchored links in forum signatures, dofollow signature links and forum with low advertising are the factors that are considered.
I am telling you from my personal experience when i find solution of anything related to marketing and traffic I stop at the forum and check the replies and then register and contribute. Maybe you should work more, post content and add good categories that are of high interest for people such as marketing, traffic, content, trade, software etc and then post good content. I have seen some good new forums taking off, they offer cracked software. You just need a goal and work on it.
Forum marketing is a great way to get traffic to your website, but only if it is done properly.Make a few accounts. Login using several computers and browsers to make the forum look active. Display your gratitude as well as say thanks to those who have assisted you.