One of the best tools for window cleaning isn't -- contrary to what many of us use -- a roll of paper towels but, rather, a squeegee. It's what the pros use, and properly using a squeegee to clean the inside of your windows won't make a big wet mess. Let's talk about technique.
First you need to choose the right size tool for your space, and for the windows you're cleaning. You'll do fine washing most windows with a 10- to 12-inch (25.4- to 30.5-centimeter) squeegee, and for windows that have muntins (those strips of wood or other material that make up the grid of a divided windowpane) or skinny windows, get a custom-fit by snipping the metal ends of an improperly-sized squeegee so there is quarter-inch (a little more than half a centimeter) gap between each end and the edge of the windowpane [sources: Family Handyman Magazine, D'Agnese]. Attach an extension pole to your squeegee for windows too high to reach.
Although you probably won't need to wash your windows more than a few times a year (if that), you can still put your squeegee to work; use it as part of your bathroom-cleaning tools to clean a glass shower door.