The keywords meta tag expresses the content or body of page at hand and should reflect keywords specified in the content areas of the page. There are two approaches that I suggest people to create their tag cloud for Keyword meta tag.
First approach is to write your content and put your ideas on the paper roughly. Put all your thoughts once, even don’t miss the ones which you consider to be least important for that writing. Then narrow down your purpose of writing and try to give your written content a very comprehensive Title or try to present your whole theme in just one line. After writing a heading for your article, now it’s the time to pick up keywords from your heading or comprehensive title that you have written. Make a comma separated list of keywords that you extracted from your title and put them in your Meta Keyword tag. If you are not able to come up with more than couple of keywords then you should also think in terms of synonyms or words matching your main them and put them in meta as well but do remember that those selected keywords should be at least present one time in body of your article or content.
Second approach is the reverse of above. Think of your main theme and keywords first about which you are going to write and then write your article revolving around those keywords. But remember your writings will be read by humans so don’t ever try to only think crawlers and robots in your mind and how they are going to rank your page. If you have written a quality article which has sufficient keywords in body, title and in meta then people would naturally link to your website and you will eventually enjoy the higher rankings.
First approach is more comfortable and appropriate for people who don’t know about SEO or have a basic idea of it. It is also recommended to use lowercase text to better match search queries. For example:
<meta name="keywords" content="ebooks download, electronic downloadable copy, downloadable ebooks, pdf ebook downloads, pdf downloads, free ebook download”>
Try to avoid repeating your main keywords in the same fashion more than three times. It is best to change your terms using plurals, breakings, and mis-spellings. Don’t use the trademarks and brands of other companies in keywords.
Although the significance of meta tags for search engine rankings has declined, it is still vital to write a good description meta tag because search engines like MSN and Yahoo prefer the description meta tag in their SERPs. Google is least concerned with description tags for calculating SERP position. Google looks for other factors too while calculating the relevancy of content. But its good practice to always write meaningful and relevant description meta tags. If there is no description tag specified on any page, search engines create their description starting with the very first paragraph of content displayed on the page. Description meta tag should be at most, 300 characters long.