Simply put a little shampoo onto a cloth or even your hand whilst your in the shower and rub it all over the glass. You can rinse it off if you want to but there is no need. The glass with be clean and steam free. I do it all the time.
Buy an E Cloth from B&Q or the net and rub over the glass, it doesn't need to be wet at all and will remove waterstains etc.
I'm a housekeeper and I love that cloth!