Up until 3 to 4 years ago, I had never done anything other than use wax. I watched this guy's series of videos:
I then bought a Porter Cable Polisher and kit with pads and compounds from this website:
Porter Cable 7424 XP Dual Action Polisher - dual action orbital car polisher, car care kits, buffer kits, PC 7424,7424XP, 7424 XP, porter cable
The results are incredible.