How do I properly caulk a bathtub or shower

Start by removing all old caulk using a caulk remover tool or utility knife, then clean the surface thoroughly with rubbing alcohol or a mildew-killing cleaner and let it dry completely. Fill the tub with water before caulking so the tub is weighted down, which prevents the caulk from cracking later when you use it. Apply painter's tape along both edges of the joint to get a clean line. Cut the caulk tube tip at a 45-degree angle, load it into a caulk gun, and apply a steady continuous bead along the joint. Wet your finger or use a caulk smoothing tool to press and smooth the bead in one pass. Remove the tape immediately before the caulk dries, then let it cure 24 to 48 hours before using the shower.