Great article here on the subject.
Most important bit of information is to rinse the windows thoroughly with water before touching them. Will rinse away any of the larger bits and pieces that will cause scratching of the window.
Also very important, is NOT using glass cleaner. Assuming here that you have acrylic windows, and the ammonia contained in most glass cleaners will cause crazing (very tiny cracks).
The best option for cleaning acrylic windows is actually your bare hand, and cleaning with a cotton rag (old t-shirt). The article linked above contains more of what not to get on your windows than it does of what to use, which is far more important in my opinion. A few bugs left on the windows is far better than a ruined window that requires replacing.
Hope that helps.