Use one of the lesson plan formats from the FOI handbook. Also, be prepared to write a lesson plan during the oral part of the checkride. When I did my initial CFI with a Fed he gave me 30 minutes to prepare lesson plans on transition to high performance aircraft and spins. You should have all the reference material with you, just refer to the PHAK and Airplane Flying Handbook and knock out a couple of lesson plans. Then he had me teach one of the lessons (I don't think he was listening). During my CFII checkride with a DE, he gave me a lesson to prepare the night before the checkride. (He was listening when I taught the class to him. I would also use the control and performance method to teach basic aircraft instrument control but be prepared to explain the primary/support method, I'll bet you a jellyroll the examiner will ask about it.