When should a girl be taught the importance of a self exam and how to do one?

That's a good question. I would think that late high school is a good time to start. Just remember that teen girls are often prone to cysts that are completely benign. They need to know to start young, but not to panic if they find something. Always have it checked out, but don't consider it a death sentence!

--------------------------------------------------------------
Little teacup

Before they are twenty definitely.  I remember meeting girls in college who wouldn't even do that because they had been taught not to touch themselves. 

High school sounds like a good age to learn what to do and what to look for.

--------------------------------------------------------------
Keeping my head above water lol

I agree with the general consensus, the younger the better.  It should also be stressed that once they are twenty and adults taking care of themselves they should also begin to learn about when to take mammograms and other signs to look for.  

--------------------------------------------------------------
Finding my muse