Never spam your forum on other forums, chatboxs or by PM's. No one joins forums which are spammed... People are more likely to sign up if they see it advertised somewhere. Spamming http://www.thefootballerforum.com was not a good idea this morning as that is not going to help as to was PM advertising on there aswell. I do tend to report PM advertisers but i couldn't be bothered to report you this morning. Spamming gives your forum a bad name and will put off the people who might have joined if you didn't spam.
The guests that are visiting now are probably mostly all bots whether they are search bots (yahoo, google, msn etc) or spam bots. For the real human visitors you just need to ensure that they can see most/all of your forum and that your forum looks as active as possible so post lots of topics and get some discussions started with your other members. They will then sign up if they want to.
Also, I think you have to be patient. I only have 9 members on my forum (it's 2 months old) BUT, I have 302 posts as of today...so they are very active, and advertise! I think finding places to advertise that cater to the same subject would help too. 🙂
Spamming won't help you in the long-run. You need to put some sweat and tears into building a good coimmunity by adding content and keeping the conversation interesting. You'll be rewarded for your efforts, but it won't come easy.