I use Adwords for my main page and for Affiliate pages to help generate extra revenue. What is interesting is I can see stats for pages that my campaigns are not set for, which in return gives me more detail on what is happening on my site and how I can better optimize those pages that are attracting more visitors.
Now for the Affiliates I use Googles Keyword suggestion tool and I filter out keywords that are forbidden to use for the companies I affiliate for. For example this page: Affiliate Marketing Program Software. I did not use the company's name or software title for the page name or in title.
After a day or two of running the adds Google gives me some more keyword suggestions that I filter through and pick for better conversions.