Finding Negative Keywords
There are several good sources for finding negative keywords for your Google AdWords pay per click accounts.
Mine the Natural Search Engine Listings
The first place to start is the natural search engine listings. For your direct keywords, go to Google’s main page, and do a search for your keyword. Any site that is listed in the top 100 results that is not directly related to your website is a source of information. Figure out why Google thought that site was related to your keyword, and what negative keyword would cause it not to show in a Google search result.
Google AdWords Sandbox
The second tool is the Google Sandbox. Place your keyword in the Google AdWords Sandbox and do a search. The more specific keywords section lists the phrase keywords that your ad will be shown for. If any of these keywords do not relate to your site, determine what negative keyword will cause that phrase not to show. If you use the expanded broad match option, mine this section for more negative keywords.
When you have built your entire negative keyword list, run your keyword with the negative keyword through the Google AdWords sandbox again to see what keywords will trigger your ad.
The third tool we recommend is mining your own referrer logs for what queries were used to find your website. If you do not have access to server logs, we suggest you look through our Traffic Analysis Software to find a suitable package that will run on your server.