Here's a wonderful and quick tip for Renoise users: read the wiki. There is an insane amount of useful information there that will help you learn and understand the way the program works and operates.
Specifically, read up on the audio devices, how they work and what each parameter does. This will only benefit the way you use Renoise to generate your sound. I'm browsing through it right now and I'm even picking up little things here and there about how some of the effects work.