...and, if you don't use soap, you can't get soap-scum. Use detergent-based products especially in hard-water areas...that's liquids like shower gels etc. If, however, you're talking about white chalk deposits from hard water, then use a drying blade to remove water before it dries and wipe down with a weak acid...vinegar, lemon juice or weak citric acid from crystals (very useful to have in a hard-water area)
Forget the branded cleaners products, get down to Wickes and get yourself a T scraper (it's got a 4inch blade with a T shaped handle) used with care it'll shift anything.
!Only works on flat surfaces though!
Diddly....if you don't, then the scum and crap just builds up. The joy of using something like Mr Muscle shower spray is that its spray and rinse....no scrubbing needed.
I haven't got a shower but I use it on the bath and it works a treat !
Agree with TigerLady about Karcher Window vac. No OG, it's not a steam cleaner, it's a type of rechargable vacuum cleaner, perfect for glass and flat tiles.
If it is really bad make a paste of washing powder and apply with a sponge (I bought a cheap own brand product) leave for a few minutes and then rinse off. The glass sparkles. Then I agree with others, dry after every use and apply shower spray.