Avoid Direct Sunlight
No matter which supplies you use, avoid cleaning windows when the sun is shining directly on the glass or when there's a warm, dry wind. While you might yearn to see the sun to shining through your newly crystal-clear window, if the glass warms too much while the windows are wet, it'll dry the cleaner before you've had a chance to wipe the window clean. You'll be left with spots, streaks and film -- not to mention a lot of the dirt you meant to clean off in the first place.
Adapted from "101 Old-Time Country Household Hints," © 2008 Publications International, Ltd.