You don’t want to waste your time and money building a product no one will want to use or pay for. So, first get out of the building and talk to your customers. But there’s a world of difference between talk and action.
It's also vital to know what the most important metric is to your business right now. That's because one of the most precious resources a startup has is focus, and spreading your attention across dozens of metrics gets in the way of learning. Ben and Alistair call this focusing on the One Metric That Matters (OMTM), and it's a core theme of the book.