Windex is trash. No really--throw your Windex in the trash.
Easy peezy pumpkin squeezy...1:4 ratio of vinegar to water in a spray bottle and viola!
You got yourself a no-streak shine! (elbow grease not included)
Spray directly on glass or mirrors and wipe with a microfiber cloth. Or, if you're as poor as we were growing up, old newspaper will do.
The Recipe: Glass Cleaner
Do I really need to spell this out? No, but here goes:
Fill spray bottle 1/4 of the way with vinegar.
Fill to the top with water.
Daaas it! She go!