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.)