assuming its just tape popping off....
- furniture out
- drop cloths or resin paper on the floor
- remove the popcorn from the entire ceiling, smooth look is much cleaner anyway.
- removed the tape along the popped joint
- clean out the crack and reset any screws or nails that popped.
- apply compound to the crack (ample not excessive, less is better.)
- apply the new tape
- apply another coat of compound over the tape and smooth it all out
- let it dry, and while it dries you can wash the compound out of your ear (i dont know how, but a big glob always manages to find its way in at least one ear...so annoying)
- sand it, and reapply compound if needed and re-sand until it looks like glass
- dont be afraid to spread the joint 1 1/2' wide if you need to.
- paint it BLUE
now everybody has a different way of doing things from different parts of the country, so im sure someone else will chime in with their way. this is how i have done it since day one with no problems.
if you really like the popcorn you can rent a sprayer, or for the more noticeable and cheap way, its available in aerosol cans for doing just the immediate area. i always say that popcorn is for hiding a piss poor sheet rock/tape job, but thats just my opinion.
also, taping comes with practice, so it may be worth having a buddy around who has done it before who might have a helpful word or two while you are doing it.