I agree with Jim about Bill Kershner's Flight Instructor Manual. This is a
book that you can get real world examples of how to teach many primary and
advanced lessons. It's one of my favorites and can be used for years after
you take your checkride.

The FAA will want you to know and be able to apply and regurgitate their
mantra, word for word. You MUST own, study, learn, and be able to teach
from the FAA books. Some FAA Inspectors and even some DE's have been known
to dismiss all information found in any other sources. So start with the
FAA info, then back it up with materials from some of the industry's better
authors.

You'll need copies of all the PTS books, and I'd suggest all the ASA Oral
Prep books also.

You should also start a 3-ring binder and download all the FAA Advisory
Circulars, I think Matthew Waugh's site has a list. He also has a great
list of CFI material, links, and books.
http://home.nc.rr.com/mwaugh/Aviation/index.htm

Make sure you have the latest versions of any books that you buy. Don't buy
out of date material from amazon or ebay.

A very real part of being a CFI (and one that the FAA wants you to realize)
is that you need to know where to find answers to students questions. If
the answer isn't in your head, it better be in a book that you own and you
should be able to show the student.

Jim