CFI Oral Prep
No amount of book work, lesson plans, and mad studying will prepare you enough for the oral. Just when I thought I knew what I was doing, I'd meet with a very experienced CFI/DPE and do a mock oral. It was during these mock orals that I would realize that I didn't know enough.
My advice, just as everyone else recommended, study the materials AND do ground school oral prep with a qualified individual. That person can reflect to you the areas you need to strengthen, and it is good practice for presenting your lessons and fine tuning the "teacher" side of you.
Good luck!