Use a broom to brush off any cobwebs. Brush off the dust from any screens on the windows because if they remain dirty, your windows will get dirty again in no time. It is best to remove the screen first, clean it, wash the window and than install back the window.
Make a bucket of soap water using any detergent that you want, which could be your dish wash liquid. Some people add vinegar or ammonia to the soap water to make the solution more effective. Take a large sponge, dip it well in the soap solution and clean the windows with it in wide circular motion. Narrow areas like the corners are hideouts for duct and dirt and this is where you should concentrate.
Dip the sponge in clear water now and rinse it to get off the soap from it. Wipe it again on the window pane now, this time to absorb the soap layer. Rinse the sponge again with clean water and repeat the process. Do it till you are sure you have taken off all the soap from the window glass. A garden hose can make your work easy here. Spray the column of water unto the glass and wash off all the soap. However, this is of course not possible for inner windows unless you have emptied the whole place.
A squeegee is a professional tool used by window cleaners. Use a squeegee to wipe off the water from the glass pane. Use vertical strokes first, covering all parts of the pane. A final horizontal stroke will remove all the water accumulated at the base. By cleaning up the excess water, the squeegee eliminates any chances of water streaks. Use a paper towel or clean cloth to wipe dry the small areas missed by this tool to achieve perfection.
The above steps apply to both inside and outside windows. What different you can do on the inside is to use a glass cleaner on the windows and wipe it clean with a clean cloth to make your windows sparkle.