My forum is on the first page when you type in "animal crossing forum" into Google (and near the top of the second page when you type "animal crossing forums)! I just noticed that today! I'm so happy!
New content is what brought mine up. Have news about the game posted as soon as you can find it.
Mine took months to beat out an old article on blabbermouth.net (the largest rock/metal news site), but it finally did about 3-4 days ago.
Just having it active with new material will keep it up or bring it up some. Also having the link in various places on the internet should increase your google ranking.
Get quality (not quantity!) links to your site with the text being the keywords you want to appear higher for.
Search engines analyse the link text of links to a website to guess what it is about. For example if you have a lot of links to your site with the text 'Free photos' google will assume your site is about free photos.
(of course google is far more complicated than that but it gives you an idea)
Don't do one or the other, there are different practices you need to put into effect to get it ranking higher (although forums are becoming increasingly harder to rank due to most being spam and so many forums are covering the same content and subject. You need to be better then any other forum in your field, get links, get content, get activity for regular crawling and use other sites such as; Twitter to post updates and such.
I'd recommend Search Engine Watch for some awesome tips and tutorials on the world of SEO.
