When your business is booming, it’s easy to take customers for granted. You have so many of them that you don’t fret when one or two drop off or abandon their cart.

But don’t forget how valuable repeat business can be. Marketing is expensive, after all. Keeping regular clients happy isn’t only sound business — it’s also healthy for your bottom line.

If you have an email system in place for customer management, it’s time to identify those old customers who are in danger of becoming ex-customers. Here’s how to do it.

Why Customers and Leads Disappear for No Apparent Reason at All

As much as businesses want to know what’s exactly going on inside a customer’s head, violating that kind of privacy just isn’t technologically possible yet — and it’s probably illegal anyway. The simple truth is that you can’t always know why a customer dropped off after buying from your—or nearly buying from you.

Maybe they…

• Deleted all of their bookmarks and lost your business in the shuffle

• Found a competing business that offered a better deal once and haven’t switched back

• Suddenly discovered Dave Ramsey, converted to Frugalism, and no longer include you in their monthly budget

• Simply changed emails

In a worst case scenario, your relationship with first-time customers is like a first date. Maybe they’re simply not that into you.

But there’s good news: it’s just as likely that customers have dropped you for a completely arbitrary and forgettable reason. In this case, one simple email can be the tipping point, the incentive that reminds them just how valuable you were to them in the first place. Let’s land that second date.

Step One: Identify Your “Lost” Customers

What is a “lost” customer? Let’s not forget this is a highly relative term. If you own a restaurant and see Sally and Bob come in every single Saturday, you’ll worry about losing them if they miss just one week. If you run an online service that re-ups every six months, it could take years to realize you’ve lost a customer. How important is this identification process? According to the Harvard Business Review:

Simply identifying those who are the most likely to sign up again, rather than appealing to every defector, can increase win-back rates eightfold.

To create a specific email template that targets lost customers, you first have to define your parameters.

It’s up to you to decide what’s best for your business — and what will bother regular customers the least. But here are a few suggestions for sending out a “lost customer” email:

• When full shopping carts are abandoned

• A customer who makes semi-regular purchases but hasn’t been around in six to eight months

• Customers who sign up for price alerts but don’t take action It’s important to take each situation individually so that your “lost customer” email goes out in its appropriate context. The objective here is to avoid getting loyal customers to unsubscribe from your emails while enticing those who do have interest in your site.

Step #2: Write an Attention-Grabbing Email Headline Specific to Each Lost Customer

The headline here is really half the battle.

But what specific elements make up a customer-winning headline? As BetaOut.com notes, it’s important to personalize it. “Dan, we want you back” is more likely to grab my attention than “We want you back.” Even if I consciously realize that it’s just a trick of automation, I appreciate the extra effort it took to give the appearance of personalization.

Another key: don’t talk to lost customers like they’re still new leads. As Robert Cialdini notes in his famous book “Influence,” few marketing techniques are more powerful than the concept of reciprocation.

The gist of reciprocation: if people feel they “owe” you one, it’s a powerful motivating tool. How might you employ it in this case? By using a personal, less formal tone. It gives off the subtext that you already have a relationship with this customer (which is true) that means something to you (also true).

Using these two techniques, let’s rewrite some common “win-back” headlines:

• “Have you seen our latest sale?” Not good. It looks like every other promotional headline you send out. Try “[First name], where have you been?” In the email, you can then explain the latest sale that they would have missed out on.

• “Your shopping cart requires action.” This sounds more like an automated notification than anything else. What about “[First name], you left your shopping cart here”? The personal message sounds more like you’re simply asking them to clean up after themselves. Check out this “shopping cart” email from Kate Spade and notice how enticing it is. Not only do they start their headline out with “Psst…”, but they offer you a discount just to complete your purchase.

Keep these two basic lessons in mind when you write your headline and you’re sure to see an improved click-through rate.

Step #3: Give Them Something!

It’s well-known in the world of business that new customers are far costlier to acquire than old customers. Your previous customers have a relationship with you. They’ve received your goods or services, they’ve seen how well you treat them, and to a certain extent, they’re pre-sold on what you have to offer.

They’ve given you their business. As we saw with Kate Spade’s example above, the concept of reciprocation should go both ways.

In short, give them a reason to come back, even if it’s simply an announcement of a sale they might like. Some companies go so far as to create unique coupon codes for lost customers. This is a powerful way to say that you like to reward loyalty. Many customers will stick with you simply because they know that eventually, if they do, they’ll be rewarded. So reward them!

Tools for Regaining Lost Customers

If you already have an email and shopping cart system in place, you’ll find plenty of tools for identifying and seeking out lost customers via email.

• Shopify offers help with abandoned cart emails specifically.

• AWeber provides tips for keeping people from unsubscribing to your email list.

• GrooveHQ’s email templates for getting back lost customers will guide you as you draft your new set of emails.

Whatever your chosen tool or method, keep in mind just how valuable return customers are. They’re the lifeblood to companies like yours, more important than your morning coffee, more vital to the bottom line than Excel. Treat them right.