I've used many products over the years including Windex, Stoners, Invisible Glass and Sprayaway, but lately I've been trying Zep products because they all seem to work well. Zep has a heavy duty spray windshield cleaner that works really well.
When I clean my windshield while on the road, I use a small nylon scrub pad to clean the bugs off as I spray on window cleaner. Once the bugs are off, I clean one more time with the spray cleaner.
If I have a really problem window, I will use newspaper to dry with. The newspaper is the best, just can be a pain.