Here's a recipe for a small but powerful remarketing campaign using AdWords. The mission is to salvage some of your visitors who abandoned their shopping carts.
Step 1 - set up individual remarketing code snippets for your shopping cart page and your thank-you page.
Step 2 - create a custom combination audience that INcludes everyone who visits your shopping cart page but EXcludes anyone who actually completed a purchase.
Step 3 - create a dedicated campaign to target that audience with followup ads.
Step 4 - monitor conversions. This campaign will likely be small compared to your AdWords account as a whole, but there's a good chance that its conversion rate will be better than your account average. If yes, the campaign can likely support higher bids.
A campaign like this is most effective if your shopping cart remembers people's selections from one visit to the next. If your cart forgets people's selections within a certain number of days, keep that in mind when setting your cookie length.
AdWords's default frequency cap is unlimited, but I recommend setting a low to moderate cap. For one thing, your CTR will be stronger if your ads aren't overdone, and the goal is to achieve a courteous reminder about your products, not make the user feel stalked.
It will take some experimenting to find the most effective balance between various tweaks. I find that for remarketing campaigns, it works well to bid aggressively but set a low frequency cap. That ensures visibility for the ads with the target audience, but not so often as to become annoying.
Some people advocate featuring special discounts or other offers in your remarketing ads, but think hard about whether that's wise for you. Besides the obvious fact that discounts reduce profit margins, remarketing discounts will teach customers over time that they'll be rewarded for delaying their purchases. That might not be a pattern that you want to establish. Test your remarketing without gimmicks first.
