I put up a test page for a niche C++ library I had developed, but haven't actually gotten around to selling it. I do keep getting a lot of e-mails from people who are interested in it though. But making sure the thing compiles on a lot of target platforms (especially Linux) is a hassle. So, what I've found, is that people need to be able to find you (duh). Try and figure out what the most likely search terms are for the problem they are solving and make sure you rank well there on Google. That'll get you 90% of the way there.

Which product are you selling?

If you wait until it's perfect you'll never sell a single copy. My advice is to launch it, get the money going, and use that to refocus your efforts on the edge platforms on which it won't compile.

People find us 100% through Google