Don't worry about using the Meta Keywords Tag. Search engines have publicly stated that they don't look at it.
The single most important meta tag today is the Description tag. It has some weight as a ranking factor, but more importantly, it often determines (along with the Title tag) how your listing will look in the search results page. And that affects how many people will actually click on your listing. I recently wrote a blog post about this, you can find it on my website. Direct link may be even up there, right above this message.
Meta Description and Keyword tags are important. Although SE says they dont bother about Meta Keyword tags but i experience it still mad difference
meta description is still very important because that is how the search engine knows what your page is about.