I am in the process of writing something about making MyBB templates more SEO-friendly, hoping that maybe someone else will port the knowledge to phpBB or SMF soon. Anyways, I'll give you some hints.
- If you can edit the Title in the templates, add a slogan. *FORUM NAME* is bland, so you could add *FORUM NAME* - *SLOGAN*. Title tag is very big for SEO.
- Study header tags (h1, h2, etc.) and the paragraph tag, and see if you could integrate it into your forums somehow.
- SMO (Social Media Optimization) also could be very useful in driving in people to your forums, so watch out for that.
I've attempted to install the phpbb seo mod but theres always a few lines of code missing when I get half way through. So i'm not sure. Thanks for the help though =)