"A quarter cup in a quart of water makes a good window cleaner.
A reader adds: When you use vinegar in your water to wash windows, dry with newspapers. Your windows will sparkle"
The mix I use is 1 part vinegar to three parts water. I put it in a spray bottle and it works wonders. (Ummm, I don't really measure, though, I just "guesstimate" it. I haven't had any problems.)