Since I've never learned to slide (whereby you can control yr. speed), I need to get off the board before getting to the speed where I can't get off and remain vertical. For now I'm just skating gentle slopes and carving. No (well not much) bombing.
I wear Loaded gloves with hockey pucks velcroed to the palms. Cliff Coleman, downhill speed legend, told me that when you fall, remember 4 words: "Get On Your Hands." Meaning get those hockey pucks sliding on the pavement so you're not sanding off skin. Also be on your knees, i.e. knee pads with hard surfaces, so you're on all fours, sliding on hockey pucks and knee pads. The one time I had the presence of mind to do this was in San Francisco late at night when my board hit an unsurmountable crack in the pavement, and I skidded along on 4 noncorporeal surfaces. Felt pretty good about that.
Boards shown from my, ahem sponsors: at left my Santa Cruz (not sure of model)----for bombing and sharper turns, at right my Loaded Bhangra, which I ride most of the time for mellow downhills, smooth turns.