Use 1/2 cup ammonia for every 1 gallon of warm water.
Here are 14 handy formulas to create your own homemade window cleaner from Waynet.org.
Basic cleaners can make windows clear and clean without the need for expensive commercial products. Both ammonia and vinegar make suitable low-cost window glass cleaners that can cut through fingerprints, dirt and hard water spots.
Wash windows on an overcast day or when direct sunlight isn't hitting the glass to prevent streaks. Although homemade window cleaners work well, they can still cause streaks if the solution dries before you can wipe away the dirt.
Tip: Don't combine ammonia and vinegar in the cleaning solution. Ammonia is an alkali and vinegar is an acid, so the two cancel each other out and become neutral, losing all cleaning power.
Get more vinegar & ammonia window cleaning tips at Homeguides.sfgate.com.