If you need to ask this question, you should hire someone to do your on page search engine optimization and really all other forms of online marketing.
Retail e-Commerce has a great article up on doing this and how to avoid being sent into oblivion on Google's search results. They reference the recent issue that J.C. Penney had with using "black hat SEO techniques".
Hit the jump for both the article and also another describing in depth what happened with J.C. Penney.