I think that technique shouldn't be taught.
I often see players become obsessed with getting their technique perfect, when all it does it hinder your brain.
Look at Tim Henman this year, he has just concentrated on being aggresive and don't think about anything, and let it come naturally. His groundies have improved loads and thats through his simple thinking.
I have never had a lesson in my life and have my own technique that I understand.
Technique is over-rated imo.