Ask HN: What has been your most AND least painful selling experience?

By 'selling experience' I mean someone paid you for a product or service you provide. What lead to that sale?

I'm not a salesman, and I've only had painful sales experience (selling B2B), which included a lot of following up, promising more than originally intended and never are both parties completely satisfied. It's as much fun as sh^^^ing blood. I'm definitely doing something wrong.

Would really like to hear about how the HN crowd pursues sales, especially in industries with long sales cycles.