How to sand drywall without making a huge mess?
 

I need to sand a patch that made in the ceiling. A pretty big section. I have been putting it off since it's going to make a huge mess if I sand it. How can I do this without creating a major mess?

A damp cotton bath towel. Rinse frequently.

Vacuum sander. You don't even need to wear a dust mask.

A simple one like this one works fine:
http://www.acehardware.com/sm-fibatape-and-reg-vacuum-drywall-sander-sv303u--pi-1289091.html

You need to clean the vacuum filter very regularly, with any extended use, but it is so much better -- and faster -- than sealing off the repair area and cleaning up the dust afterward.

Edit: You also should need very little sanding if you've applied multiple coats of drywall mud and feathered it out properly with a wide trowel.