Preventing soap scum build-up is a lot easier than cleaning it up, so consider using a squeegee on shower walls and doors, a soap like Zest and/or using a towel to dry off the walls and doors. If you have tile walls or frosted shower doors, using a light coating of lemon oil on them periodically will help stop the growth of soap scum. And, if you have a porcelain tub, you can try to prevent build-up by applying a light coat of boat or car wax to the sides (never the bottom) of the tub. It will take some elbow grease to get rid of existing soap scum. You'll need a degreaser to cut through it. You can get a good alkaline soap scum remover at a janitorial supply store, or you can try a handful of automatic dishwasher detergent dissolved in a bucket of warm water. Make sure you cover the affected area completely and let your cleaning solution soak for at least 15 minutes. Applying this solution right after a shower is a good idea since the walls will already be wet. After the appropriate soaking time, you'll need to use a stiff scrub brush or a white, nylon-backed scrub sponge to clean the walls. You may need to soak and scrub a couple times to get rid of all the build-up. Once all the build-up is removed, make sure you rinse well. You'll need to use acid cleaner only once in a while, with the soap scum remover being used more often. Remember that overuse of strong acid cleaners on ceramic tiles can cause grout to deteriorate.