Move furniture out of the room, or out of the way to one side.
Cover with plastic and masking tape all electrical outlets, light fixtures, ceiling fans, furniture and any other items that could be dangerous or damaged by contact with water.
Cover the floor with plastic sheeting and masking tape. Secure the plastic a few inches above the baseboard so that it will catch water and debris rather than letting it run out along the edges.
Turn off electricity to the room by flipping the breaker switch that controls the flow to the area where you are working.
Put on goggles or eye protection, dust mask and any other protective clothing you wish to wear.
Spray a small area of the popcorn textured ceiling, about 4 by 4 feet, with water using a garden sprayer or spray bottle. The ceiling should be saturated, but not dripping wet.
Wait about 15 minutes for the acoustic material to soften.
Scrape away the popcorn acoustic material using a putty knife.
Repeat Steps 7 through 9 on each section of the ceiling until all of the popcorn texture is removed.