One of the best things I did when I was younger was to practice falling off. I would find things of variable heights and jump off of them teaching myself to try landing feet first then tuck and roll as I landed on the ground. Of course this was practiced on grassy areas, but I was teaching myself to react without having to think first.
When one is flying through the air in the beginning they are not thinking coherently what-so-ever. A curse may fly from one's mouth and the brain screams "This is going to hurt!"
A checklist?? An unseasoned rider (as in hardly any falls) won't remember it until after they have fallen, assessed the damage, and have picked themselves up off the ground.
By practicing in a safe environment I trained myself to react defensively without having to think about it and once my body was conditioned to respond then I could almost think and follow a checklist. (Almost)
At any rate if a person could condition themselves to crumple or roll away on impact it could save their joints and bones from a jarring landing, a flat landing, or getting trampled.
Of course terrain has much to do with it, but practicing ahead of time also helps one tone down the fear felt during a fall so that they could try and factor something like that in to the landing.
Once I felt comfortable, I practiced coming off my actual horse on the grass. First at a stand still, then in motion. Anyway, that is what worked for me and it has helped in many of my falls. Some of which could have been very nasty had I not reacted the way I did.
Having said all of that, I am older now and don't see myself jumping off of things to practice
but I do plan to refresh my crumpling skills this spring because I know I could come of my new gelding, its just a matter of when.
I ride with a helmet too.