All the above are good and I agree. They seem to emphasize teaching absolute beginners.
Once they are able to fall, a couple of hints that I think are important to (re) emphasize.
1) Breathe. Don't hold your breath. For my own training, I purse my lips and "hiss" the breath out in order to ensure that I don't hold my breath. Every couple of years I forget this, take a fall while holding my breath, and regret it.
2) Tuck your head. Probably the most important safety feature. Worth reminding.
3) Watch your foot. As you commit to the roll, look at your opposite foot. This will ensure that you tuck your head and it helps to build the right structure, and to ensure that you're committed.
4) Do not cross your feet. Looks really cool, enables you to do a very pretty, very smooth roll. But sometimes (1 in 10,000? whatever, the proportion is too high for comfort) your upper heel will land on your lower shin and shatter it. I believe that this happened to a friend of a friend this past year. Make a habit of always landing with the "upper" leg in front.
Couple of other ways to reduce the intimidation for students who can do breakfalls, but need more.
1) Uke gets down on all fours, lifts one hand and extends it under his chest to the opposite site. Partner grasps hand and pulls (smoothly, sharply) upwards. Uke flips over and smacks the mat.
2) To transition from low falls to high, shake hands with your partner, who does a 180 pivot and then holds while you take the fall over. Start low, then work high.
And of courseArt of Ukemi (Other links invited)