Mud and sheet rock that is. We got the ceiling put up in the back room this weekend! It was a fairly long process, but it looks so great now, it was totally worth it (says the wife that mostly just watched as her husband and father-in-law did most of the work). If you've never put up sheet rock before, I'm not sure I would suggest starting with a ceiling, it is one of the most challenging sheet rock projects since you have to hold it up while trying to get it secured to the ceiling. To demonstrate what I mean, why don't we look at some pictures?
You can put the screws up with just a simple drill (cordless would definitely be the preferred type), or if you're like my father-in-law and have friends with fancy tools, you might be able to borrow a cool dry wall specific tool that helps you put the screws in quickly and efficiently. You can kind of see what it looked like in this picture.
To mud and tape you first put a nice layer of mud (mud that you buy at the hardware store that is, don't just go make some mud with dirt out of your back yard) down the seam where the two pieces of sheet rock meet.