Cleaning your own windows is absolutely achievable, below are some tips to help you out.
What equipment do I need?
The basics tools you need to clean your windows well are:
It is best to buy equipment from a window cleaning company, as inferior products will give you a finish to match.
Guess that stain?
There are multiple stains that may be clouding your view like:
While many stains can be cleaned with a simple household detergent, your window cleaner may also use specifically designed scraper or a scourer. Be sure to clean de-staining tools thoroughly so they are ready to use next time - so you don't accidentally add to the a insect stain some cooking fat from last time you washed your windows.