I wrote a very short book (50 pages). I used to give it to people for free. Some people read it, some would not.

Then I made a small change.

I still give it to them for free, but I tell them that they are required to read the book before we can do an introductory lesson.

As a result, I don't have to convince anyone that I'm a good teacher, the book does that for me. I don't have to sell anyone anymore. People come in ready to sign up. Best thing I ever did.

Tiny change, huge impact.