Swaraj - 1:36 pm on Apr 26, 2010 (gmt 0)
Well, I will say that the question you have asked is wrong, because until you open a forum no one is going to get an idea about your forum opening. Start with a few topics related to that niche.
Nowadays, social networking sites are in a boom, so try to create your community their by helping others and communicating with them create a group and add members to it. One you are popular in few popular sites, just spread a word on your community about your new forum and ask your members to join there. Put a section for your community discussions on your forum as well so that your social communities members will be in touch there as well.
One you get consistent members and discussions on the forum, you won't have to do much. All your members will do the rest of the things. If you have a good capital base try to purchase space on some popular sites to place your forum banners.