1. Find a suitable domain name here (e.g. realgm.com):
http://www.networksolutions.com/domain- ... esults.jsp. You should put a lot of thought into this and find a name that is easy to remember.
2. Have the domain hosted. I use these guys for the sites that I maintain ($4.95 a month, unlimited bandwidth):
http://www.webhost4life.com/webhost4lif ... osting.bml. The Windows hosting does support PHP/MySQL, which is what you'll need if you want to run most of the popular message board applications.
3. Design your website, or hire someone to do it for you. You can get some good templates here, then plug in your message board:
http://www.templatemonster.com/4. Download and configure PHPBB (you'll have to read the manuals, but it's not too terribly difficult -- just time consuming):
http://www.phpbb.com/5. Advertise. Research SEO and make extensive use of Google's Webmaster tools.
Edit: The goal of sites like this is to generate a ton of traffic so that you can pick up advertisers. Once the site is up and running, you'll want to use Google Analytics to track page views. This is free up to a certain point (depends on traffic I believe) and incredibly useful. People often wonder why so many retards are allowed to post on these boards without being banned, but it would be counter-productive to get rid of posters. Also, managing a popular forum is extremely time consuming and you'll no doubt enlist moderators to help you. The good thing is that if your site is popular then you will get lots of volunteers just because being a mod makes some people feel privileged, while others do it because they have an interest in keeping things tidy.