Find cracks in the ceiling. Cracks are caused by a variety of factors, including settling and earthquake damage. Small hairline cracks should be inspected to make sure they are not the result of a serious problem, but they are usually not an indication of a falling ceiling. Large cracks could indicate an unstable joist above the drywall, destructive settling or other damage. This instability could cause portions of the ceiling to fall.
Look for discolored marks on the ceiling inside your home. This is a sign of water or other damage, which could indicate that the drywall is beginning to weaken and that parts of the ceiling could fall. Repairing the source of the leak will prevent the water from saturating and spreading to larger portions of the ceiling. As water saturates the drywall and the damage spreads, a larger area of the ceiling is likely to fall.
Identify holes or breaks in the ceiling. This is a sign that portions of the drywall are damaged and could loosen from the joists. This damage is usually isolated to one or several pieces of drywall, but rarely will cause the entire ceiling to fall.
Look for fallen ceiling tiles. Tiles lose their adhesion to the drywall as a result of water saturation or physical force such as a earthquake. This could be a sign of a larger structural integrity issue and could indicate problems with the drywall or joists.