I find the best practice to use the version you prefer and what works best on your site and rankings. Then try to get backlinks with the other version in the linktext. For example you use the plural version on your site, you should get backlinks with the singular version of the word. Hope this is helpful!
use the singular version...use both infact bt chose that which is more relevant acc to the current post.. use only 3 -5 keywords in a post... To rank your website on google first page generate the organic traffic via forum posting,directory submision,blog commenting,socail bookmark sharing site.. forum posting nad directory submission is most imp as it helps in incresing traffic and creating link.. do blog commenting on sites similar to your website niche.. make your content fresh and unique...above all a blooger need patience and consistence in his work.. Happy blogging..hope it helps you..
Using only one of them will have VERY bad effect on your ranking. Use different phrases as well as some generic ones.
Nowadays Search Engines are more intelligent than before enough to understand singular and plural forms. It's nothing to keep thinking about which form you should use in your site META. Just go with any form. Also META Keywords are old school now. Keywords from your content will work not from your META Keywords anymore.
Both. Keyword phrases such as the singular and plural forms of your words, which are related, are extremely simple to use within the visible copy on your pages. When we naturally write or speak, we use both plural and singular forms of words, so why restrict yourself to one or the other?Never optimize a page or a site for just one keyword phrase. That is the equivalent of SEO suicide in my opinion. Every site has hundreds if not thousands of phrases that someone might use to find it. Figure out what they are, and then use them to your advantage to bring highly targeted visitors to your site.