You have to know who those first users are and how you're going to get them. Then you're going to sit down and just have a party with those first few users and focus entirely on them and making them super super happy.

One YC startup building a mobile email client had a beta group of exactly one user: Sam Altman. Sam uses email constantly and knows every client option, so he's sufficiently demanding — if the product makes Sam happy, odds are it will make lots of other people happy too.

One of the things we tell startups in these extreme cases where they can make just one user happy is to act like a consultant. Act like Sam has hired you to make an email app just for him — it can say 'Sam Altman' at the top of the screen. That's ok! Just so long as Sam would feel bummed if you stopped working on it. That's the test.

Intensity beats breadth at the start: a small group that loves you is worth more than a large group that's lukewarm, because the small, intense fire is what spreads.