Scrape the popcorn texture off
Skim coat the ceiling with joint compound
Sand the ceiling smooth
Prime the ceiling
Paint the ceiling
Install drywall over the popcorn ceiling
Screw drywall into the joists
Tape and mud the drywall seams
Sand, prime, and paint the drywall
Install ceiling planks
Install beadboard panels
Install tongue-and-groove boards
Install wood or faux-wood beams
Install ceiling tiles
Install a drop ceiling grid and tiles
Cover with fabric panels
Hire a professional for asbestos testing before disturbing the ceiling