Don't drop it on the car and you'll be fine. Seriously, that's about the only way to really screw up your finish with one of these.

What pads did you get and what polish do you plan on using? I'm a Meguiar's fan myself and get all my stuff at autodetailingsolutions.com Using either M80 or M83 with a Meguiar's yellow polishing pad I've been able to get rid of most any issue I've come across. I rarely pull out my rotary unless I'm trying to remove wet-sanding marks from something.

For polishing purposes you want to use a speed setting of 4 or 5, but physically move the machine slowly over the surface of the paint. No fast back and forth motions, let the machine work. Apply a fair amount of downward pressure too, not enough to stop the pads from spinning, but almost. Of course, that sort of depends on which polish and pads you use - I know Prima polish on a Lake County pad works better with very light pressure but the opposite is true of most Meguiar's polishes. Of course, the paint itself has a lot to do with technique as well since different paint systems respond differently.

I suggest you check out the forums at meguiarsonline.com and read up on all this.