Cracked plaster?

If you have a plaster and lath ceiling/wall with a few short, tight cracks, repairing them is probably smarter than covering them. But if cracks span the entire ceiling/wall or the plaster alongside the cracks feels loose when you press on it, making lasting repairs is tough. Plaster cracks often come back, even after careful repairs. Overlaying the plaster with drywall is the best way to be sure that the cracks don't come back in a year or two. 

 Old popcorn ceiling?  

Do you want to remove or patch a popcorn ceiling? First, remember that removing a popcorn ceiling is a really dirty job. Second, patching a hole is just, well, patching a hole. You should consider simply covering the whole ugly mess with a new layer of drywall instead. It’s probably the easiest way to get the best results 

Water damage? Is it better to repair or replace drywall?

Depending on how large an area the damage covers, and also how extensive the damage is, the drywall may simply be dried out and repainted. ... Because water damage generally affects a large area, replacing the damaged drywall will almost certainly be necessary if the damage is extensive