Effectively, you're looking to do customer discovery. What you want to do is ask questions to learn more about the problem your customers have - save your solution in the back of your mind but understand what they are trying to accomplish.

Justin Wilcox's 5 simple questions helped a lot but practice makes perfect: https://customerdevlabs.com/2013/11/05/how-i-interview-custo...

Here's a link to additional resources: https://medium.com/lean-startup-circle/all-the-resources-you...