Ask HN: How to promote an API to developers?

Hello everybody.

Anybody willing to share some advice on how to market an API to developers?

Until now I had to drag nearly every user by hand into my service[0], so I was wondering how other people do it.

Since I am experimenting a bit with google adwords, I would be happy if somebody could share his API-project and how many clicks they have to pay until they get a signup.

Do you monitor web forums to see if problems occur that you can fix? How do you tell those users then without being spammy?

[0] http://template2pdf.com/