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:
Fulfillment Services
Full-Service Internet Fulfillment.
“Complete Our Form Online Now”
Free Webinar
Search Engine Optimization
“Register Online Today”
Here is an example of ad copy for an ecommerce call to action:
Trendy Clothing
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.