I'm don't claim to be an expert, but...
1) Keep the speed low (start at 1000-1200 rpm, no more than 1500 rpm until you get some experience)
2) Keep the machine moving, but moving slowly (4 inches per second is just about right)
3) Use light pressure (high pressure and speed burns paint)
4) Gripping the machine by the head rather than the handle often makes it easier to control
5) Give the polish time to break down, but don't buff to long (once the shine starts to come through, it's generally a good time to stop)
6) Buff up to egdes, not on them
7) Keep the pad reasonably flat, and try not to drive the outer edge of the pad into other painted surfaces
8) Use mild compounds and foam pads to start with
9) Clean the pad occasionally with a dull screwdriver to keep it from loading up