Basic practice when optimizing for more then one keyword phrase is to have a specific page for each phrase you want to optimize for. If you want to stretch it, you may be able to optimize for up to three keyword phrases. But typically you do not want to go that route.

Jill's HighRanking's Forum has a thread named How To Do Seo For More Then One Phrase? In that thread, Jill and friends explain why its not best to try to stuff all your keywords on one page.

(1) It is hard to optimize for an unlimited number of keywords on one page.
(2) If you do succeed in ranking well for all of those keywords, when the end user lands on your homepage for that keyword phrase, it is much harder to drive them to a landing page that they can convert on. Why? Because the page is also targeting dozens of other keyword phrases that may not relate to the one they came in on.
(3) Managing uncontrollable changes at the search engines is much harder.
(4) The page will not read too well.

And other reasons, forum discussion at HighRankings Forum.

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