Some advice that can be useful for software sales too:

It’s much easier to just borrow other peoples’ audiences when you need them.

Try emailing prominent bloggers discount codes for your software — you then can borrow their audience if they are willing to publish your discount codes just like the linked articles says (for getting “beta” users).

Run some cheap tests

Though this only applies once you have an idea, I thought it was an excellent suggestion on using Google AdWords to run ads based on your idea to see if there is some interest in the  idea.