One thing he doesn't talk about that fits really well is Steven Blank's Customer Development model, which essentially is: don't wait until you've built your pro

One thing he doesn't talk about that fits really well is Steven Blank's Customer Development model, which essentially is: don't wait until you've built your product to solicit feedback. Get out there and start talking to your (hypothetical) customers NOW. Show them your internal version, show them mockups, sketch it on the back of a napkin, do whatever you have to do. Don't keep waiting until you have "something to show" before you start getting feedback.