If you have a tiled bath, check the caulk bead along the top edge of the tub or shower pan; if it's cracked or missing, water can seep behind the tiles and destroy the wall. Here's an easy way to apply a new bead: First, dig out all the old caulk with a thin-bladed screwdriver or putty knife. Brush out any dust or debris and allow the open joint to dry. Then apply two straight, parallel strips of masking tape — one on the tiled wall, the other along the top edge of the tub.
Squeeze a thick bead of caulk into the joint and force it into the crack with a wet fingertip. Wipe off your finger, wet it again, and smooth out the caulk. Then carefully peel off the tape strips to reveal a neat, straight bead.