Which is the best approach to keep safe during a thunderstorm?
Stay inside a big building or a hard-topped metallic car.
The best approach would be to be aware of the weather forecast and the possibility of thunderstorms and stay indoors. It is a good idea to be inside a big building or a hard-topped metal vehicle. But if you do find yourself out in the open, crouching (NOT lying down) might be of help to reduce the height. We want to keep our body's contact surface area with the ground to a minimum; plus, keep the height as low as possible. But crouching is still not foolproof.