Better Gas Milage Tips?

I own a 1994 Audi and i'm looking for some good tips on conserving gas and getting better gas milage. Also i was looking at some websites for ways to conserve gas and i need some help anwsering this question. It says on the website to roll up my windows when i'm at highway speeds because of the drag and that the drag can reduce my milage by 10% and i'm just wondering if i had the air conditioner on how much would my milage be down and if its accually worth it to roll up my windows and use my ac or not.