Most startups are not just built for the person who is using them. When you do that, every now and then you get really lucky and... are representative of some huge class of people who all want the same thing you do... but very often that just turns into a side project that doesn't go anywhere.

Users think they know what they want, but you get the horseless carriage effect where you're getting asked for a faster horse.

The most interesting things you learn in an interviews come from the: 'interesting', 'tell me more'

This is true for most new products. The majority of people you're competing with are non-users. They are people who have never used your service before. And what they say is actually the most important. What they say is the thing that blocks you from expanding the size of your market with your features.

Recording interviews is like magic. a) It stops you from taking notes in the middle and b) you can play that recording for people.

I wish I could tell you the recipe for figuring out who the target user is for your product and who your users should be, but... there isn't a recipe. It comes down to think really hard and use your judgement to figure out who you're really building this for.

Who you talk to is just as important as what questions you ask and what you pull away from it.