I admit that I tend to do a lot of stuff for no charge when I have the time. The extras that I do tend to be one of two types. First type is something that is quick, easy, will be noticed and won't be repeated constantly. Stains, a light scratch, small amount of road paint behind the wheel. I try to avoid things that will be repeated by the customer. If they or their kids constantly trash the same areas then I just do the normal cleaning. The second type would be something that would benefit me in some way. It could be something that I just can't stand and have to take care of. Some of my weekly customers I wax a panel or two as I have time. It helps keep the car in nice shape and is a little easier to wash. Other day I did a light interior cleaning (few spots on seats, top areas of carpet and mats, clean majority of trim) for free on a wash. It wasn't even a regular customer. My benefit is although they don't get their car cleaned often, they are one of two people in a business that I depend on. They make my life easy by getting everyones keys and money before I get there. I have a few places that I deal with one person only and try to hook them up when I can.
Some customers also get hooked up when I get a new product in and I want to try it out.
Some customers also get hooked up when I get a new product in and I want to try it out.