I used to teach swim lessons as well, and I was a lifeguard for a long time too. The first thing we always start with is floating - practice floating on your back, and on your front. Try to fill your chest cavity with as much air as you can, and flutter your hands at your sides to help keep you afloat. This will get you comfortable in the water, and floating on your stomach will help you get confident holding your face in the water. Once you're confident floating, teaching swimming is nothing more than adding arms and legs, teaching breathing rhythms, and perfecting it. Good luck!!