Congratulations! Since it sounds like you'll be doing this in the US, if you want to get a jump start on your studies, grab a copy of the "Aviation Instructor's Handbook." It's an FAA publication upon which you will be required to take a written test. A portion of your oral exam for your flight instructor certificate will cover it as well, and they will be looking for your instruction to follow the formats contained in that book.
You may want to slam a couple Red Bull drinks before opening that book, as it isn't exactly a riveting read!