One important component in good ad copy is having a call to action. When a searcher sees your ad, you would want to direct them to your call to action (what you would want them to do on your site once they click). If a completed lead form or an e-commerce transaction is your goal, this should be stated in your ad copy.
Here is an example of ad copy for a lead generation call to action:
Full-Service Internet Fulfillment.
“Complete Our Form Online Now”
Search Engine Optimization
“Register Online Today”
Here is an example of ad copy for an ecommerce call to action:
Great Holiday Gifts for You’re Teen.
“Buy Online Now”
These have clear examples of what you want the user to do once they’ve reached your website.
Of course along with a strong call to action you want to direct traffic to a relevant landing page. The ad copy should direct the user to the landing page that has a clear call to action i.e. a lead form page. This could potentially increase your quality score in Google and eliminate irrelevant traffic as well. Remember it takes more than a call to action to have strong ad messaging. The ad copy should also describe how the keyword is associated with the product/service.