Adding the right tags can make a world of difference when you are designing your lens. This can greatly help your traffic in two ways. It can help search engines find you by highlighting your most important keywords, and it can also generate traffic from withing Squidoo through Squidoo searches and the "explore related pages".
To help find keywords related to your theme I recommend using the free SEO Book Keyword Suggestion Tool. All that you do is enter the main keyword that you want and hit submit. Then you are provided with a list of related keywords along with estimated daily searches on each term in the major search engines.
You can use these search terms to either help you come up with new ideas for contend in your modules. Or, you can edit your existing content to incorporate these new keywords. After a few days to weeks, you should start noticing more traffic to your lens from the added keywords.