I have had the highest Post Click Conversion rate when I create several very targeted Ad Listings for each Ad Campaign.

Ad Words allows you to orginize your Entire Campaign into:

1.) Ad Campaign - Which you can only have 25 per account.

2.) Ad Listings - Which I have not found a limit to.

I create Campaigns with general catagories and then create targeted Ad Listings for specific Key Phrases.

Example:

To target the Grosvenor Hotel in san Francisco I would create a Ad Listing in my California Campaign for the Grosvenor Hotel San Francisco. I would use all targeted key phrases for the Grosvenor Hotel in San Franciso and The Ad Listing(Ad Box you see in the SERPS) will be specific to your search terms.

This has the greatest Post Click Conversion for my clients. The closer the title of the Ad Listing to your target Key phrase the higher the CTR.