This is the process of CLEANING a window. - It's not funny... because how the hell do you make window cleaning funny?
First you need a squeegee. You can purchase a REAL squeegee from your local hardware store. Look for a brand name such as Ettore or Unger. Some of these will still be consumer grade so try to find one that looks like this:
If you can't find one there, you're screwed and you fail at life... or you could try another store. Whatever, Captain Hero who's too cheap to just hire a window cleaner.
Next you need your cleaning "water" or solution. While I would recommend a professional (shock) solution, you can get by with dish soap and water. You only need a few DROPS of dish soap for a gallon of water. I mean a FEW DROPS literally. Literally means, I said exactly what I mean. If you put too much soap in the water you'll end up making your windows worse. Don't be that guy.
Your applicator. For this you can use a dish towel. A professional scrubber is recommended but we've already established that you're a cheap bastard since you're here reading up on how to do it yourself anyway. The Ettore Golden Glove(tm) or Porcupine work terrific. You can purchase a scrubber and a t-bar to hold the scrubber for about $10-$15 online. Google is your friend... so they say.
Apply the solution to the glass using your applicator. If using a dish towel, use circular motions, turning to a clean section of towel often to help avoid moving the dirt around on the glass and potentially scratching it. Hell if I know if circular motions work better but it worked for fucking Karate Kid so it'll god damn work for your money-saving lonely ass.
Use either the squeegee tip or a dry rag to wipe either the top or the side edge of the glass to create a "dry channel". This is where you will begin each squeegee stroke. Yeah Beavis, I said stroke.
This seems like common sense, but since you're probably just shy of getting a handicap placard... Remove the solution from the glass using the squeegee. Start at the top or the sides and pull straight across the glass (or straight down). This is called a "straight-pull" and it is how most window cleaners start. After each swipe of the squeegee, wipe it on a cloth. The cloth can be dry or slightly damn. Repeat the squeegee motions until you have removed the liquid from the surface of the glass. Grab a beer, you're almost done.
Use a dry cloth to wipe the edges of the glass. You can do this while they're wet or dry but either way, if you don't wipe the edges, where the glass is held in place by the window frame, you could end up with a dirty line on each edge. Just wipe them. I think it's easier when they've dried but to each his own.
Congrats, you've just saved about $5. Now clean the other 20 windows in your house the same way, being careful not to fall to your death from a ladder and you'll have saved $100 or more! Put out of your mind that what takes a window cleaner an hour to do will take you an entire weekend. Crank the Nickleback and get to work cheapskate.