PRO: Brent Weingard, owner, Expert Window Cleaners, New York City
SECRET: To remove grime on divided-light windows, cut a metal-frame squeegee so that it fits a pane, says Weingard. Take out the rubber blade, and use a hacksaw to trim the metal channel ¼ inch narrower than the pane. With a utility knife, cut the blade to the pane's full width; fit the blade into the channel so that it projects 1/8 inch at each end. As with any window, spritz, wipe with a sponge or a microfiber cloth, then use the squeegee. "Most people skip the sponge part, but that's the only way to really dislodge the dirt," says Weingard.