Know What You're Getting Into
If you own or have stumbled onto what you believe is a museum-quality glass piece, don't try to clean it yourself. Although a soft, slightly damp, lint free cloth may work for minor dusting, anything more aggressive should be evaluated by a pro first. A professional conservator will know how to clean and dry your glass without causing damage. This qualifies as one of those "Don't try this at home" situations where you may end up very sorry you spritzed that vase with commercial window cleaner and let it air dry on your countertop. If you have a piece you can't afford to lose, have it evaluated before attempting to clean or repair it.
If you're trying to maintain an heirloom-quality piece, wiping it down with distilled water regularly should be enough of a cleaning regimen. Without specific instructions to do so from a professional, avoid submerging quality antique glass in water, and keep the water you're using at room temperature or just slightly warm.