Assuming you’ve already got a fair amount of content, here's how to increase the rank strength for your chosen keywords without the need to re-write your website code or site architecture. If you’re just starting your new website take note to save yourself redoing it in the future.
The idea is to allow search engine spiders to flow freely through your site using a keyword (and variants of that keyword) as the anchor text to direct the spiders to a chosen landing page.
Example: if I am trying to rank highly for the keyword “Top Twitter Users” I will create an article on the Top 10 Twitter Users. I will then find which of my existing pages I can link to my new article from and place a hyperlink on those pages using the anchor text Top 10 Twitter Tips (and variations of that).
Choose Your Keyword
The first thing to do is pick your keyword and 2-3 variations of that keyword.
Google AdWords Keyword Tool is a great site to help you determine how many searches a specific keyword gets and provides you with variations of that keyword.
With this tool you can also find out how much competition your keyword has and what the search trend is like (i.e. Are more people searching for that keyword than 6 months ago?)
Pick Your Landing Page
Select which page you want to target to be found when people are searching for your keywords.
Choose your best article on the subject and not your homepage.
If you don't have one invest some time in writing a great article on the subject that people will be interested in reading and is relevant to their search.
How much content do you have?
Determine how much content your website has for your chosen keyword.
This is straight forward to do: in the Google search box type [site:yourwebsite.com keyword] (remove the brackets when doing this).
Make a list of the top 10-20 results (URL’s) that are returned.
Now add a link from each of the pages that were returned for your search.
Mix up the anchor text a little as well. Use variations.