Get professional-grade window cleaning results by following a professional-grade cleaning technique. Begin with a scrubber such as a soft sponge, natural sea sponge or a cloth-covered head on a squeegee, a bucket of warm clean water (your "dirty" bucket), and a bucket of warm water with just a few drops of liquid dish soap in it (if your blade squeaks like an old wiper blade on a dirty car windshield, you need a little more soap in your mix). Dip the scrubber in the soapy water and squeeze out any excess suds. Scrub one window at a time.
Begin cleaning the window with your squeegee. Start at a top corner and pull the squeegee down in a single straight stroke; repeat downward strokes, and dry the squeegee blade with a lint-free cloth (not a paper towel, which will leave lint on the blade) after each stroke. When all vertical strokes are done, pull the blade horizontally across the bottom of the window glass to clean up any remaining drips [source: Martha Stewart].