Having an updated, detailed record of customer data is critical for retaining and growing your customer base. But the real challenge is to figure out which pieces of data provide the insights you need to make better business decisions — and proactively prevent customers from leaving.

Eleven entrepreneurs from Young Entrepreneur Council (YEC) share what types of customer data they find to be most important as customer growth rate increases.

1. Track your Net Promoter Score.

We ask all of our users, “How likely are you to recommend our product to a friend or colleague (on a scale of 1-10)?” Then we use this data to calculate our Net Promoter Score, or the percentage of promoters (nines and tens) minus the percentage of detractors (ones to sixes). We always follow up to the question with a “why?” and we get lot of really important insight from this simple question.–Mattan Griffel, One Month

2. Keep an updated record of all contact information.

Whether you’re running a website or a brick-and-mortar, maintaining a database of your customers is one of the most important things you can do. A large part of our sales are generated by repeat customers when we reach out to them (instead of vice versa). Entice them to share their information but make sure not to ask for more than you need, as that can be a turnoff.–Nicolas Gremion, Free-eBooks.net

3. Collect user experience data.

We collect data that relates to how our customers use our hardware and our apps. First, this allows us to prioritize the features in a UI and create a better user experience. Second, we can use data to determine which functions are more popular. We then use this data to prioritize new feature rollouts or certain functions over others. Data is a great way to create better and more meaningful experiences.–Andrew Thomas, SkyBell Video Doorbell

4. Understand the purchase decision hierarchy.

Learning what influences the purchase decisions of current customers can be a great tool in retaining their business. They may be working with you because of cost, convenience etc.; learning what is most important to them will position your business to keep delivering value. You may also be able to determine the best way to get new like-minded customers from your discussions with current ones.–Charles Bogoian,Kenai Sports, LLC

5. Learn how they discovered your business.

As you continue to grow organically, knowing how customers found your company is a good measure of the effectiveness of your sales and marketing teams. You can also tie this back to data, including the lifetime value of a customer by source, which will help you correct your path to effective marketing.–Ania Rodriguez, Key Lime Interactive.com

6. Find out why they left.

While it is, of course, important to track points of data while someone is using your service, we find that the most critical piece of data is finding out why customers have moved on. It is impossible to eliminate churn, but we can always be improving it. So, we send follow-up emails to everyone that quits our games to find out how we can improve the experience, and it has worked wonders.–James Simpson, GoldFire Studios

7. Analyze their buying behavior.

The key to driving higher sales is to understand your buyers’ purchasing behavior. You should classify buyers into an “active” and “dormant” status. Your active buyer status bucket may include anyone who has purchased within the last 30 days, while your dormant groups might be broken into buyers who haven’t purchased in 30 days. Once you have the groups defined you customize marketing messages accordingly.–Obinna Ekezie, Wakanow.com

8. Keep track of Twitter followers.

We use Intercom for customer interactions, which lets us track our customers’ number of Twitter followers. When we’re looking for people to feature in customer case studies, we reach out to customers with high follower counts — they’re more likely to share their case study and tell people how happy they are with our product. It’s important to find and interact with our most influential customers.–Jared Brown,Hubstaff

9. Determine what level of decision-making power each lead has.

Are they a CXO or a junior analyst? Knowing whether or not a lead is in a decision-making position helps our sales team score and prioritize their leads better. We have an in-house LinkedIn plugin that pulls in the designation of a lead from LinkedIn and assigns a score for seniority.–Pratham Mittal, VenturePact

10. Look at their last sign-in date.

This one piece of information helps us target customers who are slipping away, which is key to reducing churn. If it’s been awhile since a paying customer last signed in, we can reach out to them and find out if they need our help. We also use this data while users are in their free trial period to get constructive feedback from people who tried Hubstaff once or twice and didn’t continue to use it.–Dave Nevogt, Hubstaff.com

11. Keep track of their physical address.

Something often overlooked is their actual physical address. Customers change their email address far more than they would change where they live, so if you have that amongst your data, it can be useful for many years to come. And sending them the occasional letter, holiday card, or thank-you note is something customers appreciate, which allows you to have communication beyond the traditional avenues.–Kumar Arora, Aroridex, Ltd.