Take what Tstordiver wrote and combine it with a solid prescriptive learning/teaching program such as PADI’s and from the onset resolve to be conservative with your student ratio and not cut any corners.
Safety first.
Finally consider; that although we love the sport and want to pass it on to as many people as possible... The sport is not for everyone. In some cases the best thing you can do is be honest with a student who would present a danger to themselves and their buddies.