Be sure to determine whether you are talking about popcorn ceilings (blown on, sometimes with dangerous asbestos added) or a knock down orange peel texture coat.
Once you have tested popcorn for asbestos (check with your local building and safety department as to how to go about this safely), the coating is very easy to remove. Do a test spot to determine if a raw, rough coat of plaster lies under the texture, or simply drywall. If it is drywall, then remove texture as described below and allow to dry thoroughly before adding a microthin layer of plaster skim coat followed by paint.
The method we have found most successful in removing popcorn ceilings or textured walls is as follows. First we remove everything in the room. We lay down a drop cloth of kraft paper that is backed with plastic, kraft paper side up to prevent slippery accidents. Then we take a very cheap deep nap paint roller and get it moist, not drippy. In a paint roller tray we mix about 5 parts of wheat wall paper paste to plain water and a tiny squeeze of liquid dishwashing detergent. (For you chemistry buffs, we have just created a colloid suspension and a surfactant.) We roll the gooey mixture onto the ceiling ( or wall) making sure that every inch is covered. Then wait 15 minutes or so in normal weather. Take a one gallon garden pump sprayer (have an extra replacement pump part at hand in case the first one wears out). Pump a fine spray of water onto a square yard of area and allow it to soak into the gooey mixture, reactivating it. Do a second square yard, then go back to the first and start scraping with a broad edge putty knife. Re-spray as necessary, never getting drippy. By the time you finish area one, area two is ready for scrapping, and so on. Never goop up an area and leave it for more than a few minutues to take a break.
If the orange peel is stubborn, gentley scrape it with a wallpaper removal device called a paper tiger available at most hardware stores. This rough-toothed plastic wheel takes off just the very top coat of orange peel, allowing the water and gooey mixture to insinuate itself underneath texture and paint, forcing it to peel off.
When everything is removed, go over all surfaces with old towels or teeshirts and plain water to get all soap and goop off of surfaces. This step should not be eliminated...a clean dry surface is needed to plaster skim coat or paint.
The beauty of this system is that it is relatively dust free, the undesirable texture rolls off onto the drop cloth like morning oatmeal, and folds up in the drop cloth for easy disposal.