If you are doing remarketing on your website (which you should, if you are not), then you should take a look at this article which gives some really good tips on drawing attention to your ad to get a better click-through rate. A better CTR means more visitors and a lower price you have to pay, so it’s a win-win position you want to be in.
Read the full article here:
Get them Clicking! 4 Banner Ad Design Tips to Improve Conversion