The very first thing you want to teach your student when giving flying lessons is how to do the preflight checks on the airplane. Your student should know what to look for in preflight checks and what to do if there is a problem found while doing them. Only after your student can do a preflight check correctly can you go on to actual flying. Of course at first you will want to start out simple and easy with the flying lessons being sure not to overload your student on the first day. Just learning how to taxi down the runway and takeoff and fly a level flight is a lot to learn. Of course you will want to teach them how to descend and land the plane as well. You should be sure to go over what the post-flight procedures will be after the flight as well and make sure they can do them accurately.
As their flying lessons go on you should teach them more about the communications and introduce them to flying by instruments. It will also be important that they are taught emergency procedures as well so they can respond to an emergency if need be. Also as they progress you can teach them how to achieve touch and go landings and how to land in bad weather conditions and without some of their gear.
As they learn more and more eventually in their flying lessons you can take them on a cross country flight being sure to show them how to open and close flight plans and teach them what to do if they do not have communication with the tower. They should also be taught to fly cross country using navigation techniques and also how to fly at night. It is your job as an instructor to prepare them in their flying lessons to take the flight test and to help them become successful.