It's also in the legwork. Just posting alone isn't going to get you anywhere. it's always a combination of methods. self posting, "hired" posters, are a good start. Then again, the key is to determine WHO the people are that you feel are the right ones for your forum, your target group. Go to where these people are. Talk to them about it, present them with an option to be with their peers, direct them to your board. the legwork is in direct emailing, cross posting on other, likewise minded boards, press release (if your forum presents press releasable content), etc. there are tons of ways to promote, most likely to succeed is the way that utilizes all of them.