Here's what I've done. My forum has been up for about 18 months and currently has about 15K members, 25K threads, and 200K posts, and gets over 200K uniques per month.
* Forum Topic - Make sure you have a topic that is in some way a new niche that will draw people. I don't get the point of trying to compete with WHT or some other huge forum by opening one that is identical and then trying to get people to go there. People want to go to busy forums. You really need to find your niche and then stay the course... promote it, exploit it, etc.
* Forum Organization - Don't create too many forum topics to start. I did this and it was a mistake. You end up with a ton of empty forums. I now start with a high level consolidated topic... then target a point when I'll split it into more topics. For example if you had a forum on cars... you might start with Sports Cars... then after you get 100 threads, you break it up into American, Japanese, and European Sports Cars. Then when any of them hits 100 threads, you break it out into Ford, Chevy, and Chrysler (for American) Sports Cars... then wait for them to grow.
* Moderators - You need about 4-5 active people who will moderate, or at least help build the discussion in each forum. They need to be up for posting something every day until it takes off. Its a must, or the topics will die. I look for people that are real active, and then discuss being a moderator. They need to be very helpful.
* New Member Area - Create an area where new members can start off, and make sure you keep a close eye on it and reply right away.
* Search Engines - What ever forum script you use, make sure its search engine friendly. As the forum grows, each posts is another indexed page.
* Promotions - Talk to companies that have products related to your site and offer to do reviews in exchange for 3-5 free copies for your forum members. Then promote it and drive posts. I was successful at building over 1000 threads in about a month on a brand new product that has a huge dedicated forum focused on it. I simply gave away one of the products when it first came out, and did some advertising around it. That forum is now active, even though there is the huge dedicated forum. In the past, I was never able to build new products that had other dedicated forums.
* Helpful Info - Post tutorials, how-tos, and other useful information. You can even talk to other sites that have that type of thing and offer to post link backs if they allow you to publish some of their info. This way the search engines will index it for you and build traffic to your site.
* Other Forums - Be very careful with this, but its helpful to post in other forums helpful information and have a link to your forum in your signature. The other forum owners may not like this at all, but as long as you are being active and helpful... and not just posting links to your forum, they will probably be cool. It works best if the other forum is related, but not a direct competitor. If you had a forum called domaindiscussions, then the dnforum guys may not appreciate you promoting it here.
* Time - It takes a lot of time to build it up... a TON of time.
* Partnerships - I've found a few folks with sites that were cooperative who I've partnered with. In one case a busy news site didn't have their own forum. I added a link to their news on my site, and they agreed to make my forum their forum link on their site. I've also found companies that didn't have support forums who I've added forums for on my site, and they link to it from their support page.
Hope this is helpful to you!
