One window washing tip is to wash windows on a cloudy day. Direct sunlight causes window cleaner to dry too quickly, leaving behind streaks on the glass. Another tip is to first sweep debris from windows using a small brush to prevent loose dirt from sticking to the cleaning cloth.
When washing a window that tilts inward, spray the window well but not so heavily that the cleaner drips. Use a clean, lint-free cloth, and wipe the window in a horizontal direction until the glass is dry. Tilt the window in the opposite direction, and spray the glass with cleaner. Wipe the window vertically to make any streaks that are left behind easier to see.
When washing double-hung windows that don't tilt inward, slide the bottom pane up approximately 8 inches. Reach out and clean as much of the window as possible, and then slide the top portion of the window down to clean the glass from above.