Well there are various methods.. if you have some budget to spend that would be gr8!
First of all you will need some unique content on the forum. Hire around 10 forum posters to get things get started. You can easily buy a post somewhere around $.10/each.
Also, social bookmarking can help you gain some good backlinks and decent traffic
I'm offering social bookmarking service check out my thread here:
http://www.v7n.com/forums/services/8...0-10-only.html