This'll apply for any site, but being the top search for Google will help and be your greatest asset. This can be achieved by using metatags and title tags, although sometimes you may need to pay to improve your search rank.
Once you get visitors you have about 10 seconds to get them hooked on your site and want to join. No I'm not making that up, you have to understand that viewers want the relevant info as fast as possible. This can come down to visuals, layout, organisation of links and pages; the easier it is for people to find what they want the faster you will have them join the site.
Why is Google more popular than Yahoo, why is Facebook more popular than MySpace, what makes a brand preference to Apple or Microsoft. These are questions you have to understand and by doing so you can understand how people (consumers) will act. Copying the competition isn't always the best as well and sometimes you may need to change things up to gather more interest. That is what Mahz, the guild's site owner, has been trying to achieve. He's worked hard on creating a custom, unique experience that matches consumer's desires. It's a hard road but it has paid out well so far.