A few hints for you to have a look at before you clean your windows.
Use The Proper Tools – Use professional squeegees, soap and applicators. If you don't, your windows will look like they do now!
Be Careful Of The Sun – NEVER wash windows in direct sunlight. The sun heats the glass and will leave your windows streaky and dirty.
A Clean Scrubber – Always start the job with a clean scrubber. Rinse the scrubber frequently if you are cleaning many windows, especially dirty windows.
Holding The Squeegee – Hold the squeegee at an angle so the water runs down the glass.
Wipe The Blade – After each stroke, wipe the rubber blade with your lint free cloth.
Overlap Your Strokes – Overlap squeegee strokes by about 4 cms. Remember to angle the squeegee so water flows towards the wet window surface.
Use Lots Of Water – When first washing the window with the scrubber, use lots of cleaning water. You want the dirt to come off the window with this solution. Use a decent amount on interior glass surfaces, but not so much as to cause a flood or standing water on woodwork.
Go Sideways – Horizontal squeegee strokes are recommended when at all possible. If you are right handed, the left side of the window pane will have triangles of water left behind with each stroke. You will wipe these at the end with a final vertical stroke going from the top of the pane to the bottom of the pane.
Wipe The Edges – There will always be water marks or spots at the edge of the window pane. After all squeegee action is complete, wipe the entire window edge with the lint free cloth. Do this regularly so your windows stay clean and dry!
Practice First – Practice with the squeegee when you first get it. It may be hard to control.
I hope some of these hints and tips helped you out.