Prepare the Room
Remove furniture and items in the room.
Seal off the entire room by hanging two millimeter plastic sheets from the crown molding all the way to the floor (Image 1).
Put a window fan in the window for added ventilation.
Add a drop cloth with a waterproof backing to the floor (Image 2).
If the popcorn was added before 1979, get it tested for asbestos by either wetting down a small area with a sponge and scraping off a little to place in a small bag, or by having a professional come out and test it.