Clean windows on a cloudy, but not rainy day. Working in direct sunlight causes streaks because the cleaning chemicals dries before you can wipe it off. This is the best time to clean the frames and windows sills. Cool, clear water is the choice of most professional window cleaners. If windows are very dirty you can use Method Glass Cleaner Spray 828ml UK, or you can find other good windows /glass cleaning solution on market.
This one cost around £6.50. It is among of the good glass cleaner solution which removes streaks and smudges on glass and it has a fresh mint scent, also it is non-toxic window cleaner. Remember to use horizontal strokes on the inside and vertical on the outside so you know which side the streaks are on. For drying windows, a wad of crumpled newspaper works just as well as expensive paper towels. Wear rubber gloves to keep your hands free of ink. If you need more help ask Decent Cleaning.