The North Florida FSDO CFIs with ESP seminar is excellent--definitely catch it if you have the opportunity.
If you haven't had a chance to read it yet, you should probably pick up the seminal "Stick and Rudder," which, in addition to being an excellent book about flying, is also a great example of how to take high-level aviation topics and present them in a way that's simple and easy-to-understand.
As for other books, read everything you can. A big part of being a top-notch instructor is having a wealth of knowledge to draw upon for your lessons. While sometimes a bit morbid, reading NTSB accident reports can also be very informative.
That said, your absolute best resource is going to be other instructors. Learn from them what is and is not effective, things to look out for, stories you can use to enhance your lessons and how to deal with the inevitable frustrating situations.
If you know a CFI that will let you do so, teach a couple ground lessons to actual students with their CFI supervising.