Are you referring to the Meta tag or keywords on your page. If you meant the META tag then I wouldn't bother putting the effort into building the list. I like SEOMoz.org's opinion on META keywords that they are only good for giving your competition an idea of what keywords your focusing on.
If you meant keywords in the content of your page. I would suggest picking those that fit best and focus on making it human readable. I would be discouraged by a site that seemed to stuff keywords in the content.
