There is a very good, but lengthy guide to machine polishing on the "detailingworld forum"
http://www.detailingworld.co.uk/forum/showthread.php?t=63859
before i had a go with the DA i read everything i could and watched loads of vids...some are good and informative (Larry from AMMO), but its definitely worth going to the local scrapyard and grabbing and old boot lid and having a go on that first, gives you an insite on how much pressure to apply to keep the pad rotating.