[header] How to clean mirrors [title] Assess the condition of your mirror. [step] Depending on the location and use of your mirror, it may have accumulated special kinds of grime that need specific cleaning agents to remove. Limescale or calcium deposits are likely culprits, and should be pre-treated before you tackle lesser stains. 
You can : [substeps] Identify calcium deposits by white, slightly rough textured spots. These can be removed by white vinegar on a damp cloth.