I suggest optimizing your site, when people find you on Google or Yahoo, they will join if it looks appealing. Also, try blogging or podcasting issues that can help your search. You can send me a private message if you want to talk more about it.

Add few fresh and good contents, good articles, offer referral program, contests to attract the members.

can u guys join my forum at << url snipped >>

<< mod edit: no site specific talk please >>

I've not seen single post in your forum, how one can join your forum without a single member. You should make it live with few posts before requesting the fellow members. :-|

Get friends to join up to help you kick start with posting and activity. Apart from that concentrate on adding new content, optimizing your site for search engines. Here are a few ideas to get a few members to start of with.
1. Post on sites which have subject similar to yours and keep a link to your forum/site in your signature, if you are posting well and helping people out they will notice and will follow the link to your site.
2. Join Yahoo and MSN groups and help out people there and along with that tell people about your site but dont spam.
3. Create new discussions on your forum so that it gives people an incentive to first register and then air their views. No one will join if you wait for them to register and start discussions.

scribbller made some good suggestions.

good stuff scribbler
i have made a point thing (<<site.com>> cash) and you can earn the currency by posting or referring-and can be later exchanged for prizes and advertising

try to offer somthing to the member, somthing they will like. try to offer free email,, add a forum shop etc if you pm me your link i will try to help more

Viral marketing is also a way to go with.