Good question, luckily Justin Freeman has a detailed and comprehensive answer, including:
>No two gunpoint situations are alike, and they will all be very dynamic situations. My advice is to remain calm, be as compliant as you can, be aware of your surroundings, and do what you need to in order to survive. But the obvious best case scenario is keeping yourself out of the situation that put you on the business end of a firearm[…]
Great stuff.
[via Steve Streza]