The outside of our windows need to be cleaned a few times per year. If the weather is nice, I take a jug of Windex Outdoor, attach it to the hose and spray down the windows. Windex Outdoor has two settings... one that sprays the cleaner and one that sprays plain water as a follow-up. The windows that aren't on the 2nd story I wipe down with a microfiber towel. Even the 2nd story windows are pretty streak-free. If the weather is too hot or cold I have a company I use.
I really don't clean the insides very often, but if I do it's with Windex and a microfiber towel.
