how clean interior windshield and windows really good?

I've had my best luck with an aerosol spray that contains alcohol.....cuts oily film. Then finish with a clean paper towel. White vinegar is best on the outside of the windows because is reacts with and dissolves hard water spots.

Agree with Hornet. Aerosol glass cleaners work the best. 'Invisible Glass' is a well known brand and is available at Wal Mart and several other retailers. It is right around $4/can. I recommend using a microfiber cloth, spray onto the cloth and wipe, keep folding the cloth in on itself as you progress across the inside of the glass. Buy a multi-pack of the cloths for best results and use a fresh one after every 4 folds or so. Then save one for a final wipedown. Do not use bath towels that have been exposed to laundry softener, or high end paper towels with printing in the future. Both will leave streaks. Source: I have a mororhome with a windsheild that is approx 7.5 feet long, and 3 feet high.....

Soap and water to get the bugs and stuff off. I like Invisible Glass cleaner. You can make optical grade cleaner with distilled water, 99% Isopropyl alcohol, a small amount of Windex and a drop or two of a good dish soap.

If you are talking about cleaning windshield at the inside of the car (interior side of the windshield not its exterior), and how hard this is, I suspect you have installed vynil seat covers which emitt greasy stuff when exposed to sun. Replace with cloth covers.