Ad tracking is an excellent way to keep track of where your responses are coming from, Paula. 

When testing your ads, be sure to only change one thing about an ad each time you do a test. 

Change the headline but leave the body of the ad the same, and track your reponses to that. 

Or change the body and leave the headline the same. 

Or instead of writing a bunch of paragraphs, try making a list of benefits.

People also respond better when you use the words YOU and FREE a lot.  Pile on lots of freebies.

Numbers bring in a lot of responses also, get your calculator and figure out what your customers are getting per each penny they spend.

Also try tracking which times of day bring you the most response, sometimes advertising very late at night and very early morning may bring you new customers from Australia or Asia because they're 12 to 15 hours time difference than we are. 

Also early mornings could bring you east-coast responders before they go to work, and late nights you could be getting west-coast people.