How do I clean the waterspots off of my shower doors, I've tried all cleaners.?

This a new house and contracters were no help on how to clean wood floors, granite, shower doors and stainless steele. I have all the basic cleaners for all, but frankly.......they all suck! Especially the cleaners for my gl shower doors, like I said, I have all the basic store cleaners and I still see those ugly water marks.