It is the increasing number of members, that will ease your work. More and more members means more and more visits. And more visits will lead to you high rankings. Then you will have to do some work of directory submission.
Dear u can Do - Soical Networking - Maintain good quality of threads in forum - Maintain good quality of Post in forum also on-page and Off-page Activity
Something I've thought of in the past is automating your sitemap to auto-update as new content is posted. Since search engines use sitemaps to help them figure out where to crawl, this could potentially help, but I have no proof. Also if you check out the Bing forums you can post normally or post a "suggested answer" to a thread, which the thread-starter can select as the official answer. This puts a damper on long discussions, but makes threads more linkable because they provide actual answers. Once you have blogs or high PR sites linking directly to forum threads, there's more reason for the engines to view the forum as useful and rank it higher.
Forums are for discussions and you are allowed to have signatures in this form this you can have lot of backlinks.
Hi there, if you really want to optimize your forum site and you want to obtain an increase of visitors to it, then all you need to do is apply some seo strategies. By this account you will be able to not only increase your viewers and visitors but also increase the traffic to your site as well.
Allow user to enable signature from their first post itself. Allow user to spam by putting repeated question