Tape off and cover all electrical outlets. You do not want the textured paint to lodge itself into the outlet once removed.
Spread plastic sheets over the entire floor. It may help to tape the sheets up against the walls. You are going to use water so the sheets will help protect the floor from becoming wet. It also makes for easier cleanup.
Mix two or three tablespoons of mild dish soap into a gallon of water. Then fill a pump sprayer with the solution. You can purchase a pump sprayer at any home-improvement store.
Spray an area of the ceiling until it is thoroughly soaked. You want to make sure the texture on the ceiling is soft. Do not spray the entire ceiling at once because parts are going to dry before you can properly see to them.
Stand on your ladder and use a putty knife to scrape away the textured paint. With the ceiling thoroughly wet the paint should fall right off.
Proceed with spraying additional areas of the ceiling and scraping the textured paint off until the entire ceiling has been cleared of the texture.
Sand the ceiling to smooth out any jagged areas that may be left over from the textured paint.