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.

Twitch launched in June of 2011, and our growth ever since has exceeded even my expectations, which were not small. A year and a half later, the community of broadcasters and viewers has multiplied hundreds of percent.

The crucial people to get your product started for the first 6 months are not who will be using it 3 years later.

The other mistake I think people make is talking to who's available rather than talking to who they need to talk to.

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

The pool of people you care about is going to shift over time.

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