Some people simply don't like acoustic ceilings and want to remove them. The first thing you should do is to test for the presence of asbestos. If the ceiling was put in after 1978, there shouldn't be a problem because asbestos has been banned from use in homes.
Someone told me that it's wise to put plastic sheets over everything in the room. The plaster dust really flies. There's various ways and materials you can use to get the popcorn stuff off. Ask at your hardware store. Be sure to wear face protection and gloves. Good luck!