I find intermediate casters are the hardest to teach. The problem is THEY DON'T LISTEN, actually they listen but revert back to thier old habits as soon as they get on the water. I have many times corrected a problem only to see them go back to the problem that has been deeply imbedded in muscle memory. To correct this I teach them a practice routine, tell them to do it 5 minutes a day for 2 weeks (not while fishing), to re-educate a long time casters habits.