I recently helped somebody (adult) to learn to ride a bike, and I'm pretty happy with how I did it. The first and only thing I insisted on was how to stop, i.e. how to come from both feet on the pedals and bike moving (mostly pushed by me) to a proper stop with one foot down. Once he could do it from a reasonable speed on both sides... it was pretty much over.

I took the idea from a friend who once got on a motorcycle without a good idea of where the break was, with rather funny results. First concern should be how to stop. The rest can be trial and error.