Do a scrape test before learning how to remove popcorn ceiling
Test for Asbestos!
Prep for a big mess
Get the furniture out
Remove ceiling fixtures and fans
Protect can lights from water spray
Wet it with a pump sprayer
If the texture still hasn't softened, it might be painted, or paint might have been mixed into the texture before application. In either case, water won't easily penetrate. If the texture is painted, you might be able to dry-scrape it first to expose some of the unpainted texture and follow up with wet scraping. If the texture has paint mixed in, you might have to dry-scrape the whole ceiling or cover it up with drywall or T&G boards.
Cover electrical boxes
Work in small sections
Only spray and scrape a small area at a time—about 4 x 4 ft. If you work too large of an area at once, the popcorn might dry before you have time to scrape it off. If that happens, respray the area and wait another 10 to 15 minutes before scraping.
Tame the mess with a mud pan
Use a mud pan—the kind for holding joint compound—to catch the wet popcorn before it hits the floor. That way, you're not tracking it all over the place when you walk and move the ladder around. Also, use the edge of the pan to clean off your scraper when it gets loaded up with wet popcorn. A mud pan is available at home centers.
Round off the corners of your scraper—whether it's a wide putty knife or drywall taping knife—so it won't gouge the ceiling and leave you with dozens of ceiling wounds to repair. Use a file, a sander or an electric grinder to do this.
Scraping alone won't leave you with a paint-ready ceiling. You'll probably have small dings and gouges to fix. At a minimum, you'll have to sand the ceiling to get it perfectly smooth before painting.
Here are some tips on fi drywall and getting it ready for paint.