Over time, shower tiles collect a film of soap scum and hard water deposits, which diminishes the shine. To restore shine to the tiles, you need to remove the grime from the tile surface. Ordinary soap and water does little to cut through hard-water spots and soap scum; what's required instead is an acidic cleaner that can cut through the film. Afterward, using car wax on the cleaned tile will make the shower sparkle.
Fill a spray bottle with undiluted white vinegar. Spray the tile walls generously with the vinegar and let it remain on the tiles for 10 minutes.
Turn the shower on -- mostly hot water, so it steams -- after 10 minutes, and allow the steam from the hot water help dissolve soap scum. Let the water run for two minutes.
Wipe the tile with a damp sponge. Rinse the sponge regularly as you wipe. Thoroughly rinse the tile and dry it with a towel.
Apply 1 tablespoon of car wax to the damp sponge or a car-wax applicator. In circular motions, apply the wax to the tile starting at the top of the shower. Scoop up additional wax as needed to cover the tile. Only apply the wax to the tile walls. After the wax turns cloudy, approximately 15 to 20 minutes, wipe it off of the tile with old, clean rags. Remove all traces of wax residue from the tile.