To clean windows without leaving streaks, clean dirt off the window sills before cleaning the glass. Cleaning the sills first prevents resoiling clean glass with dirty streaks.
Trying to clean glass without cleaning the edges first can be challenging. Dirt from the sill catches on a wet cleaning cloth, so each pass of the cloth leaves fresh smudges on glass.
Step 1: Clean the sills
Use a brush or vacuum to remove loose dirt from windowsills.
Step 2: Clean the glass
Clean inside glass with spray cleaner and paper towels, wiping horizontally. Clean outside glass, wiping vertically, then rinse with a hose.
Step 3: Check for streaks
If horizontal streaks show, clean the inside glass again. If vertical streaks show, clean the outer glass again.