Start out by stretching out muscles, then warm up by starting out slow, then pick up the pace, finish off by doing crunches and floor exercises slowly.
Basic aerobics should last 25-30mins; depends what you have-jump ropes, jog/run, sprints, jumping jacks. Stations of 5/6 different exercises, spend a min. at each.
A basic aerobic lesson can be any task that elevates your heart rate for a small amount of time. Such as jumping jacks or running in place. Grouping activities together would be ideal