Even more than acquiring new customers, it's imperative to keep your current clients happy with your product or service offering. But keeping customers happy depends on knowing what they want.

So when a longtime customer suddenly leaves you for a competitor--or threatens to--don't despair. Instead, leverage the feedback of these unhappy few to identify key areas for improvement.

We spoke with 10 founders from YEC about the most effective questions to ask unhappy customers in order to get the most valuable insights. Their answers are below.

1. What are we missing?

Ask what's lacking in their experience with you, specifically in terms of what others have provided in the past. You may be failing to meet an expectation you don't even know the customer has.--Simon Casuto, eLearning Mind

2. What would make our service invaluable to you?

When an unhappy customer tells you what you need to provide in order to make your product or service something they truly can't live without, that's the key information to making what you do indispensable. It's often tied to their expectations of what they're paying for, so you can get an idea of whether you're overpriced in their eyes--that's a signal to also offer something else that's cheaper.--Dave Nevogt, Hubstaff.com

3. What could we have done differently?

Many entrepreneurs firmly believe in themselves and their product/service offering. Although confidence is needed, sometimes stepping back and asking for honest feedback of what could have been done differently, along with an open mind about change, can lead to a situation where one can improve their offerings to help increase business drastically. Happy customers mean more business.--Stanley Meytin, True Film Production

4. What did we do to disappoint you?

At College Hunks Hauling Junk, we ask unhappy clients "What did we do to disappoint you?" This helps us learn from our mistakes and correct the systems to prevent these same disappointments in the future.--Nick Friedman, College Hunks Hauling Junk

5. If you could wave a magic wand, what would you like to see?

I'd suggest asking your customers the "Magic Wand" question: "If you could wave a magic wand and change, add or do something different with our product, what would it be?" This imaginary wand gives people permission to "imagine," and therefore go much deeper than any topical answer they initially give. You'll be surprised by the answers.--Chris Brisson, Call Loop

6. Why are you still using our product?

Although the customer may be your least happy customer, they're still using your product for a reason, and it will benefit you to find out why. This question will help you better understand their priorities.--Nanxi Liu, Enplug

7. If this were your company, what would you do differently?

Giving the customer a platform to share their concerns is one of the most beneficial things you can do. There have been countless times where I had great advice for a company that had treated me poorly, but there was no medium to relay this information. It is key to ask for advice and then listen to it.--Robert De Los Santos, Sky High Party Rentals

8. What is your biggest pain point?

The customers have become unhappy because of a specific flaw in your offering--either the product or the communication. But a customer always knows their pain point, the flaw at the heart of their dissatisfaction. Empathy and humility cannot only improve your product/service, but sometimes also win the unhappy customer back by showing that you care to listen, learn and iteratively improve.--Shradha Agarwal, ContextMedia

9. What are we unsuccessful with?

Reaching out to your customer and learning where you are failing is a great opportunity. I would recommend calling the customers by phone, having a conversation and then asking them to email their thoughts. This will force them to think critically. Then, in your response, present solutions and get their feedback.--Adam Stillman, SparkReel

10. What top challenge can we help you solve?

I want to understand their core challenges and determine how we can bring them the most value. Understanding what our existing clients and potential clients deem as most challenging will help us continue to make product enhancements and transform their perception of our services into a must-have solution.--Kelsey Recht, VenueBook