Use keywords as often as possible within pages and posts.

The third aspect that search engines consider when evaluating keyword is frequency or sometimes referred to as density. How often does a specific keyword appear on your web page? The more often it appears, the more important it must be.

Do not repeat keywords. Search engines will detect that and your customers will not appreciate it. Be creative, provide lots of good information, and you'll be able to use your keywords on your website repeatedly in a normal, conversational fashion.