Search engine share your stats and you can find out how many times does the word was requested and in which region. This is important, for example, offer a service in Moscow, it is necessary to watch statistics of the given region (oblast or city). Thus you can choose popular requests its target audience. For the selection of keywords, you can use the Google adwords Keyword Tool External
of those words which were found, you can choose the most suitable. Pros contained in the text, for example: "blinds +for plastic Windows" should be removed, you get: "the blinds on the plastic Windows.
What to do next after selecting keywords:
1. To select keywords, it will be 1 selection.
2. Show for which of these keywords, your website is issued on the first page of the search and the region in which it will be 2 matches.
3. Add in your website only words of 2 stacks (List all your added sites).
keep in mind that keywords can be relevant not only the main page of the website.