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.

The question is, once you have this idea, is this enough? Is it something people would actually switch just to have?

You have this idea that you think is awesome. You want to have that broadest group you possibly can. You don't want to just talk to 1 type of person and learn that, you want to get familiar with the space.

The most common mistakes are showing people your product- don't show them your product, it's sort of like telling them bout a feature.

If you just talk to who's easy to talk to, you're not really getting the best data.

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

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.