How do I keep my new glass shower door and tiles free from scum and limescale. Cleaners never seem to work?

I have just had a new shower cubicle installed. It has white tiles and a glass shower door. In the past I have tried all the usual cleaning products and tiles and door have always ended up covered in limescale, streaks and scum. Somebody said that a product called rain racer would do the trick. Anybody used it?