If you are looking to clean anything in your home, check out this site for solid directions. The comments are extremely helpful, too. Something I’m going to do this coming weekend is take Casey’s advice:
Apply Rain – X (typically used for vehicle windows) to your shower doors and you won’t have the water spots/scum/build-up from your water. The water will just run off of the glass like it does in your vehicle. I’ve also applied a coat of car wax to my shower walls (not the floor) and it has the same effect. The water just beads up and runs off. Saves A LOT of time in cleaning and elbow grease.