Oh, most of ye are too young to remember a commercial featuring various stern housekeepers intoning, "I don't do windows!" Then the lady of the house found out Windex or somesuch concoction would clean them easily.
Windex is colored water with a bit of this-and-that thrown in. I say, "Throw it out."
Even old panes can become clear if you do these things, provided the panes are not etched. And etched panes would be rare.
First clean your panes with a lot of water from the hose if outside, a dripping sponge if inside.
Go back and use a smidgen of laundry soap in warm water and go over them again, getting the corners especially. Rinse again.
Go over and rub smudges with 90+ percent alcohol poured on a paper towel.
Now get a soft cotton rag - NOT microfiber or knit - and rub the panes with cold water and a dollop of white vinegar added. Use a very, very wrung-out cloth - and go pane-by-pane.
Get an old bunch of washclothes or a cut-up old towel, and as you clean the pane, go back over, rubbing with the cloth, buffing it dry.
Here's your secret weapon for windows with smudges that will not clear: THE SIDE OF YOUR HAND. My son kindly helped me out by being my "hand model." This is as close as he will get to actually helping clean the windows.
RUB back and forth with your hand. Go up and down on the long sides of the pane. Keep wiping your hand on a dry piece of the old towel. Use that bent pinky to get into the corners.
Don't rub blisters on yer hand, though, dearies.
For "hopeless" panes that you can tell did not come clean after the laundry-soap routine and that LOOK etched:
GET A FLAT RAZOR, as used for scraping paint off tiles and such, and use it to scrape the panes. Yep, scrape the crud right off the panes. You might see little lines of gunk as you scrape - it is working. Don't dig into your pane, though - keep the angle of attack very narrow. Then do the rest of the routine.
We are putting our house up for sale and there is a feeling in our town that panes are "etched" by our dust storms. All over town, horrible looking panes. It's not so. It's mineral deposits from our water. The razor blade treatment, combined with the final hand buff, got them perfectly clear. Neighbors are miffed. They don't WANT to do all that work. Ha.
Here's the link for a quartet of free tags, and a look-see at them. DO NOT save these tags shown here - USE THE LINK or they will not print out clear and right size.
A single web-ready image is provided, too, for decorating blogs. You can save and use it! Just RIGHT-CLICK it and save it. I like the old phone.