When recaulking a tub and shower, start by carefully removing the old caulk using a utility knife or a caulk removal tool. Thoroughly clean the area to ensure good adhesion for the new caulk, and make sure it's completely dry before proceeding. Choose a high-quality silicone caulk and apply it evenly along the seam. Smooth the caulk with a wet finger or a caulk tool for a neat finish. Allow the caulk to dry completely before using the tub or shower again.