When setting up an AdWords campaign, it is very tempting to check the box to optimize based on conversion data immediately. While you usually can’t choose CPA bidding when you start, you can check the box that says eCPC, and we see that many clients do this. However, don’t! Google’s conversion optimization algorithms need at least 15 conversions in a campaign in a 30 day period to work for that campaign. If you turn them on too early, they won’t work and can actually hurt your performance as they try to optimize on not enough data. Wait until you have at least 15 conversions in a campaign in the first 30 days to turn on eCPC or CPA bidding.
(And by conversions, I mean conversions that are registering in Google AdWords – if you have conversions from another system, Google AdWords won’t be able to see them and optimize to them, so no matter how many conversions you have, the algorithms will still be off).