You can join related forum and post your signature posts there where your forum link is your sig..

Promote your forum by submitting your forum to directories...

Yeah, same suggestion with cooluks.

To me, it is quite simple.

If you have a forum whereas nobody cares to join it; is probably not worth joining. Pursuing in its evolution into being just another forum that nobody cares to join, you'll need to solicit for meaningless new members continually.

Happy web site promotion!

You have also points on this part.

Make some link building/exchange , publish articles, work on your meta tags to fit your content - in short - SEO.

Yes I do agree with that comment. I forgot or something I overlooked to mention, the correct niche is most important key factor for SEO and traffic too. However I have seen lots of SEO doing such irrelevant links in websites of different niche.
I only wonder how could that effect otherwise PR?

Steve

The relevancy of a link doesn't affect PR. But it does have a huge affect on the search rankings.

The best way to forum is to participate in the related forum and promote that you have new site .

It seems all right, I think this is a very good way.

You have to be careful when doing that though. It's frowned upon in many forums for being spam. Since you'd be posting in other forums related to what your site is about, the last thing you want to do is get a bad reputation in your industry.

Definitely post in other forums on similar topics and link to your forum in your signature. By creating good, helpful posts, you'll gain a positive reputation among other communities in the industry, and your name and your site will become associated with quality information.

I agree with stymee, participating and posting helpful topics will really drive traffics to your forum.