Site Structure

Pages that are more than 2-3 levels deep within a website tend to achieve rank less often than pages at root level.
www.mysite.com/keyword.html versus www.mysite.com/content/pages/category/keyword.html

Site maps (linked from the home page) are used by search engine robots to easily find pages within your site.

Search engine robots follow text links much easier than image or script links so don't make it harder.

URL's that contain keywords are a ranking factor for some engines. Even if your domain name doesn't contain your keyword; you can still insert it by using a page naming methodology like this:
www.mysite.com/keyword.html instead of www.mysite.com/contentID4.html