The least effective way to A/B test ad creatives — and how most people do it — is by guessing. They change a color here, switch a picture there, try out a new tagline… but it’s all done randomly and with little direction. The better way to test is to see what your competitors and other large advertisers are doing. What colors, layouts, elements and copy are they testing? Which ads have been seen more often? Which ads have they stopped running due...