Talking to customers is one of the foundational part of building something useful.
Two books every aspiring startup founder should read.
Now, I take a different approach. I talk to my friend's friend's friends until I find the right customers to talk to. I contact my friends and ask who they know and then I ask who they know and so on. Its pretty easy once you get going. And a warm intro is an easy way to get the time you need.
Other resources are LinkedIn, Twitter, Reddit, Quora, etc. Find someone on there that has an interest in the idea you are working on. After you have a short interview ask who they know. Once you get the referrals flowing its very easy to find enough people to talk to.
A great read on this topic is Talking to Humans. A couple of takeaways:
1. Approach talking to others as a way to question your assumptions.
2. Ask for stories. People do a better job telling a specific story about their life, rather than answering hypothetical questions.
3. Look for clues, workarounds, passions, and pains.
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