Essays / The opportunity to teach something you know to someone else. Introduction? [2]

My topic is the same as the title and the want me to identify what would I teach and how would I teach that. I know how to rebuild automatic transmissions for cars, because is the one thing that I'm truly good at. I've developed the body, but I'm missing the introduction, I'm not very good at the intro. I chose that because rebuilding transmissions is very simple to do and they charge a lot on mechanic shops, and teaching that to someone else will help to save that ones money. I will apreciate any help with ideas for the intro.

Tahnks.