Everything You Wanted to Know About Selling a Course

I don't think you ever talk about actually what's in your course, and how do you decide what's good about it and what's not, or what needs to be updated. Why a course and not a membership or community (or why not that in addition)? What software do you use? Do you feel it's important for people to finish the course - meaning are there incentives and gamification to finish? Can participants get something like an amazon/starbucks gift certificate or something for referring friends to purchase the course? Have you also tried youtube ads to promote the course? What metrics do you use to decide whether course sales are good or not, or the course meets your standards or not?