Originally Posted by wphamilton

...almost every one of them threw his arm out to contact the ground first, and if you look closely some used their legs as well. It's less important though when you're only falling a foot or two like in those motorcycle track low side slides. Just sliding is great of course, if you're wearing leather, you're on a smooth road and can separate from the bike. It doesn't require special skills or training. A hint on that for those with no training: empty your lungs before impact and relax your body. Being relaxed means you won't shove your arms out in instinctive (but wrong) ways and will help distribute the shock. Empty lungs just so you don't bruise them.
@Slaninar is right, if you do have training you don't have to think about it and you do usually have time for the technique, which is not always the one you were planning btw. I'm not expert by any means, just 4th kyu but these are automatic and when you do it right you probably won't get hurt. Not road rash, not skinned hands, not bruised, no injuries at all. It's not that hard to learn basic proficiency.