Remove existing water spots by mixing equal parts water and white vinegar in a spray bottle.
Spray the solution onto the shower doors, and let it sit for five minutes to dissolve the water spots.
Wipe the shower doors with a damp cleaning rag.
Clean the shower doors after each use by either using a squeegee to remove excess water, or by wiping the doors with a dry towel after each use of the shower.
Spray the vinegar and water solution onto your shower doors at least once per week to keep the doors clean.