How did you make your community succeed? A question for active forum owners... Marketing an monetization have been the two keys to grow in my experience.
A forum is really not that different from any website. There is no secret or special technique beyond any other website... Give users something that they WANT (that they can't already get elsewhere... or do it better than any other site). For us it was our tools that already had tens of thousands of users using them before we opened the forum. For example: http://tools.digitalpoint.com/tracker.php It doesn't have to be something specific... look around at your competitors as well. Are their users unhappy with something? Give those users better options.
Yep, I agree with Shawn. Starting a forum with the single goal of monetization and use of marketing is not the right way to do it. Sure, you can get a whooping number of visitors and people to harvest money from, but will it be sustainable? You'll soon discover that good content will be ranked on top, good marketing is the word of mouth from happy users.