How to fall: Relax. Keep your hands on the handlrebars. ROtate elbow and knee out some so they hit first. "Greet the road with everything you have." And all the while, stay relaxed. I find realizing I just made a fool of my self helps.

I got to do exactly this Saturday. Road got too steep, too much gravel, I was starting to tire, couldn't get to my toestrap in time. I just got my hand back on the bar and followed my advice. Two little road rash patches on my elbow, minor bruise, a similar minor bruise on my knee and my hip definitely hit but is OK. Completely not a big deal. (Oh, I fell from a high center crown onto much lower hard clay. Level road and asphalt would have been softer.)

It works. If you cannot relax, put on some old clothes and practice on a lawn.

Edit: as a poster said above, putting down a hand is asking for a broken bone or worse. My old bike racing mantra was "don't let go of the handlebars until after you hit the road". Then yuu can use your glove palm to save skin.

Ben