1. Wipe glass with a microfiber cloth dampened with plain water.
2. For streaks, use a microfiber cloth dampened with a mixture of one part white vinegar and one part water, with one or two drops of dish washing liquid.
3. Always spray water or cleaner on the cloth rather than the mirror. (If moisture seeps under the frame, it can create spots.)
4. Use a clean, dry natural-bristle paintbrush on intricately carved frames. Starting at top of frame, flick dust downward. For gilded frames, use a sable brush, which is softer than a regular paintbrush and less likely to damage gilding.
Source https://www.marthastewart.com/266714/decorating-with-mirrors
