Beware of objects falling from the roof as you exit. Look for power lines on the ground. Some of these carry 12,000 volts of electricity. The whole group should go to a pre-designated meeting area. This should be away from power lines and objects that can come down and injure you.
Parking lots work very well.
Try your best to account for everyone who was in the building. Never re-enter a building that you have evacuated. If you have to use a phone to call 911, you may have to wait on the line for over a minute to get a dial tone. Payphone service is usually restored before business or home lines. Know how to shut off your gas and electricity.