Don't crawl. Crouch down with your feet close together and be low and rounded on top. And whatever you do DON'T get into a ditch to be below ground level.
Did you ever watch sheet lightning? Have you ever been somewhere that you can see the "stalk"? It looks like a fish's eye view of a lilly pad, with a cloud-to-ground stalk and a pad that spreads out in the clouds.
The point is that when lightning strikes the ground it then spreads out in the ground in the same fashion as a sheet lightning "lilly pad" in the clouds. If there are any gaps in the ground it will jump across them. If there is a long gap, like a trench it will jump across at the most conductive point. If you're taking shelter there, that's you.
(Similarly, as it spreads out, if you are standing with your feet apart and one closer than the strike than the other, some of the lightning current may find you a good enough path that it will go up one leg and down the other. Oops!)
The same kind of thing happens with houses, which form a gap in the ground. If you get a hit on one side it may jump through the house to reach a sump pump, well, water pipe, etc. rather than go around it. A hit nearby or on the house may result in several arcs as the lightning finds a path through various conductors with minimum (thought multiple) total airgap.
(A friend of my brother, in Michigan, had a house in the middle of a field with a ditch leading up to it. He was constantly having problems with stuff burning out in storms, since any hit on a nearby field put big voltages on his house wiring.)
Also: The charge in a cloud attracts an opposite charge to collect below it, and when the cloud is suddenly discharged (even by a cloud-to-cloud stroke) the charge below suddenly wants to run away. This creates a "surge" - a mini-version of the ground/conductive-object currents - even in the absense of a hit. It won't jump a very large gap. But it does a dandy job of frying electronic and even electrical devices.