My personal list, YMMV.

1 - Search the office for anything that can be burned to produce heat or used as insulating materials.
2 - Find any and all available water.
3 - Same as 2, but food.
4 - Cover/insulate all openings with whatever's available.
5 - Assemble everyone in one room for warmth.
6 - Crack a window, start a small fire (taking proper precautions, of course).
7 - Find any available medical supplies/ask if any co-workers have a medical condition that may be a serious concern.

That oughta be a good start.