basically, you need to use H1 tags for headers.
You must have good title pages - ie descriptive and close to what you think people will search for in google.
You must have content text in your website, stating everything about what you do and must contain the keywords that people will use to search for your type of website.
nice to have is keywords in your meta tag and a description in your description metatag.
Make sure your images are named in accordance with key phrases - eg grungy-t-shirt-new-hampshire.
make sure your in site links dont say things like "click here". (whos gonna search for click here")
off page seo
this is where you go around getting links back to your site via forum posting signatures, from fellow sites, from articles you post (links in your articles to your site), links from profiles in forums, email accounts and any other site that has profiles.
its hard to explain but google has a algo that works out which website is more important than the other.
Google also like site age
new and fresh content on your site (thats where blogs come in)
hope that helps