When you’re cleaning the outside of your windows, the weather is really important. If it’s too hot, then the water and cleaner will evaporate too quickly and you won’t be able to properly clean the window. However, if it’s raining, then cleaning it’s basically pointless. Make sure to clean your windows when the weather is right in the middle: somewhat overcast but without a forecast of rain.
I would suggest buying actual window cleaner, if you want to take this serious. It may be more expensive than making your own, but it does a way better job at keeping your window streak-free and protecting it. If you REALLY want to make your own cleaner, I would suggest a combination of hot water, vinegar, and soap.
If your windows are really dirty, then you’ll have to clean them twice. The first time, you want to just wash it and rinse it down so that any excess dirt and grime gets off. Once you’ve done that, you can clean the window more precisely. This will actually save you time (and supplies) than if you tried to do everything at once.
Some windows can be removed from the frame. If your window does this, then do that when you’re cleaning! By removing the whole window, you can clean the track a LOT better, and it stops dirt from getting spread around. Refer to your window manual and instructions, if necessary.
I think a squeegee works best when it comes to cleaning windows. Rags are good, but a squeegee just does such a better job at getting rid of all the water and giving your window that nice gleam that we all want. Again, this isn’t necessary, but I think squeegees are worth the cost.
If you DO want to just use cloths, I would suggest using a microfiber one. Other cloths leave fuzz on the window, lowering the overall cleanliness. If you use a squeegee, then I would say to just use your microfiber cloth to spot check the edges of the windows.
This may seem a bit obvious, but it’s worth noting: when cleaning the outside of your windows, start from the top and work your way down (whether the windows are right above each other or even a story apart). If you clean the bottom ones first then, when you go to clean the top ones, you run the risk of the dirty water or cleaner dripping down onto your freshly cleaned lower windows.
Some windows have hard water stains on them; that just happens if you have sprinklers near the window or other such things. Don’t waste your time trying to scrub those off—it’s not going to work and you’re going to exhaust yourself. Instead, buy hard water remover. It’s just way easier, plus it will always come in handy.