My house is rather old and I believe that my ceiling is made from plaster and not drywall, I can't be true sure but I'm almost 99.5% sure it is plaster. I have some running cracks appearing in my ceiling, maybe the biggest is a foot or 2 and is barely noticeable in some parts, it also appears to be sagging slightly around the cracks, these aren't near the edges of the wall really either. I'm curious what I could do to fix these, I'd rather do whats the best, but will settle with also temp ideas, I really hope i don't got alot of work coming up hopefully there is a decent way to fix this. Thanks for the help guys, I can post some pictures when I get home if they are needed.
When I have done this, I tear out and remove the plaster and lathe. Then re-hang drywall. This is a serious mess but is the absolute best way.
I have seen several instances (including my current home which is quite old) where someone simply slapped new drywall overtop of the plaster. Provided you screw into the ceiling joists (which would mean locating them before starting) I don't really see a problem with this. It will make your ceiling thicker, which usually isn't a problem. It was for me though when I installed ceiling mounted speakers upstairs. The extra thickness gave me some trouble with the mechanism that holds the speaker and grill in place.