This is a pretty broad question to be honest. There are different types of call to actions and different places they will appear. What they have all in common:

This is a pretty broad question to be honest. There are different types of call to actions and different places they will appear. What they have all in common: Getting a user to click on that button. I don't have any resources to recommend but you might want to look into marketing funnels and maybe sales funnels as well. Do you have any more specific questions?