Well hun you're gonna fall sometimes its a part of skating but I do have tips on how to make it less likely to happen
Keep your knees slightly bent and when going down a steep slope or off a drop bend your knees more (for a drop bend them right before you hit the ground and for a slope or hill bend your knees more as you gain speed)
If you feel. Like you might fall jump off the board (bail)
And finally if you do fall do your best to protect your head or try to roll to lessen the impact