Have you used the free Google Keyword Tool yet?
It is a great tool for allowing you to find the keywords that are most suitable for your purposes. You can search for keyword ideas by entering a keyword related to your business or service or a URL to a page containing content related to your business or service. Or, you can go straight to filtering keyword categories next to the statistics table. You can use one or the other or both together; the tool is completely flexible depending on how you’d like to use it. In Advanced Options, you can further refine your search, for example by country.
And then read: