Evacuation

The last one out of the room should not lock the door, just close it. Locking the door hinders the fire department's search and rescue efforts.
Proceed to the exit as outlined in the building's emergency action plan.
NEVER use the elevators under any circumstances.
Stay low to avoid smoke and toxic gases. The best air is close to the floor, so crawl if necessary.
If possible, cover your mouth and nose with a damp cloth to help you breathe.
If you work in a building with multiple stories, a stairway will be your primary escape route. Most enclosed stairwells in buildings over two stories are "rated" enclosures and will provide you a safe means of exit; don't panic and descend stairs slowly and carefully.
Once in a stairwell, proceed down to the fist floor. Never go up.
Once outside the building, report to a predetermined area so that a head count can be taken.