Lightning Safety - How Lightning Works
According to this article standing up is a bad idea because you are slightly more likely to get hit than if you crouch (again, only very slightly. the crouch basically does nothing to prevent you from getting hit).
The article also says that laying down is a bad idea too. So basically you are left with the lsser of three evils.
quote:
Never lay down on the ground. After lightning strikes the ground, there is an electric potential that radiates outward from the point of contact. If your body is in this area, current can flow through you. You never want the current to have the ability to pass through your body. This could cause cardiac arrest, not to mention other organ damage and burns. By making your body as low to the ground as possible and minimizing the amount of your body in contact with the ground, you can lower the possibility of a lightning-related injury. If a strike were to occur near you, the current would have a much more difficult time flowing through your body in this position."
end quote
"