Ask HN: How did you validate your startup?

How did you validate your start-up?

I recently quit my job to try and start-up and I'm in the midst of trying to validate the idea, and I wanted to know how did you guys do it?

Did you identify a target market and then call them? If so did you have a list of questions?

Did you just walk into a couple of businesses and ask them questions?

Did you follow a process that you created, or was laid out by someone else?

Also when you found someone to talk to how did you know if the problem was painful enough to charge money for without asking "how much money would you spend on this?"