What are some of the best ways of doing so? I have written a proposal and I have also sent out emails to websites trying to get sponsorship/partnership..
I can imagine it's tough because having a forum on its own isn't very special unless you have a niche. If so, study your demographic and advertise on sites that are popular for them. It has become common place to hire someone to make 'warm-up' posts on your forum so it doesn't look empty. People tend to avoid empty forums because they don't think their question/comment will be responded to, and will waste their time.
Forums are one of the hardest sites to market. Getting visitors to it is one thing and enticing them to register and participate regularly is another thing.
The best way to get a lot of guests and shizzle, is to advertise in your signature, thats a big way to promote your site. Also put it in your msn name, use FORUM EMOTIONS from your forum on other forums so that bots pick up your link.