I have used the Hunter Engineering site often in class. Most of the BMW dealers use Hunter equipment for balancing.
If you look a the bottom of the page you will see the video:
"Why does my car still shake?"
It's easier to just use the wheel balancer without doing the road force measurements so sometimes it gets skipped when the customer just asks to have the wheels balanced. The other videos on the page will help you understand what the actual process looks like in detail. Watch the "Centering Check" video also, this is where a technician can miss important details.
Hunter Wheel Balancers:
http://www.hunter.com/videos/index.cfm?cat=3
The technician needs to know the whole story to diagnosis your vibration before he starts the wheel balance. The videos may help you with that conversation.