Ask HN: How did you get your first customers?

How did you get your first paying customers, and how long did it take you to go from idea to your first sale?

Please elaborate on:

- Sales/marketing efforts that you thought would work, but didn't pay off.

- Something you wish you would have known sooner.

- The most effective way to get customers that you discovered, and how you discovered it/got it to work (for example trial and error, domain expertise, advice from a mentor, etc.)