Knowing your chemicals

I'm very new to the business with no experience in carpet cleaning before hand. My main concern is knowing what and how much chemical to use. How much prespray or soap to use? Or trying to remove coffee stains or red stains what chemicals I'm allowed to mix to make it stronger or how much I need to dilute?
Also is spraying with enzymes different than the pre spray?
I understand I have lots to learn and will need much practice on my own carpet.
Please any advice would be greatly appreciated.