Each crash is different, so Terry is right.
My basic rules are to stay loose and if possible, come to a complete stop and take stock of your limbs before trying to get up. However, if you're in the middle of traffic, there are situations where you may need to get up a bit quicker.
Sliding is better than rolling.
If you are rolling, not that it matters, but don't hold your arms out trying to stop because you'll break them.
Hi-siding all depends... I've flown off bikes so hard that I was upside down in the air, looking backwards at my bike spinning around. Coming down head-first sucks. Prayer has high value here.
In the end, common sense... Don't try to change direction or stop, or anything because your efforts are worthless. Buy good gear, make sure your insurance is up to date, and be right with God...