You can build links through article submissions, press releases, blog postings, pay per post, directory submissions, and you can also build links on this site by adding a few links to your signature while using the appropriate anchor text to link back to your site.
There are tons of soccer forums on the web. You need to advertise actively- say Adwords or other similar agencies. Buy traffic from well known sites. Get a few people to sign in there. A visitor must feel that the forum is active and not dead. Start a posting contest to attract people- you could offer a jersey of their favourite club as a prize.
more links would be a good idea on frontpage . choose the important ones from forum , maybe you can show off latest threads on the frontpage .
Link up with Soccer related Forums and Websites. Then you will get- More members More members= More Traffic
You could do revenue sharing to attract people (see sig). Add other incentives for people to take part, such as referral contests. Write to bloggers that love soccer/football. Hire a good Wordpress template designer to create a soccer theme and post it. Your link would go in the footer. Do a press release. As mentioned by downloadthenet, take part in related forums and include your link in your sig (signature). *I don't care for landing pages like that. I'd suggest having a helpful landing page, including RSS feeds, interesting articles and stories, etc. If all you want is a forum, then make that the start page.
I think before you do any of that, you should go and get as many people that you know (friends, family) and start posting like hell. It's free, and it's what people want to see when the go to a forum. Are any of your friends into football? Then chat with them. Build up a few hundred posts, then go and do everything else.
I have a high traffic soccer forum web site, however the forum itself it doesn't get too many posts... I'm going to invest on forum posting services.. do you guys know how many posters and for how long should I buy this kind of service? I have a lot of people who visit the site and read the comments etc... A few sign up but since there are a few actual users people end up leaving... By the JoHsuan.Hsu - I would trade links with you! PM me!
Advertise on Footy Blogs and other Footy sites for more members, which costs money of course ! There are loads of footy forums on the web now, so this is a hard niche you are at! I would get better opening page, it looks to plain, get a pro gfx designer to cook something up for you ! The forum could do with a more footbally skin as well! Best of luck with your forum and its future mate !