How do you know you have written the perfect? When create an Ad Group, try and created two Ads. Creating two ads will allow you the benefit of finding out which ad performs better. After a week of trailing, you can delete the weaker ad, and create a new ad to compete against the existing champion.
Measure your ads by the percentage of clicks received per impressions. The more clicks an ads receives per impressions, the more effective the ad appears to be. This technique is important for valuable keywords and can mean the difference between a successful campaign and a mediocre campaign.