During a lane change into a lane moving slower than the group (usually to the right), the FRONT bike moves over first.
Now, what do the rest of the bikes do? Legally, if the whole group moves like a "brick" (everyone changing lane together in one movement), that is considered to be parading and can cause problems if any emergency arises.
Also, if you remember from your MSF classes, you learned that you and you alone are responsible for your own safety. So, if each bike individually changes lanes in order following the first bike to change lanes (whether from the front or the back), you can reduce your risk factor, change lanes legally, and still look REAL GOOD while doing the maneuver!
It is important that the lead and tailing bikers talk to each other before the ride and come to an agreement on how they intend to pass cars.