A car would be the safest place to be at during a thunderstorm. A car acts as a Faraday cage (an earthed metal screen surrounding a piece of equipment to exclude electrostatic and electromagnetic influences) and the electrons would travel through the path that offers the least resistance which will be through the car’s metallic body and not you. Now you might think what about the rubber tires! The lightning bolt is a huge collection of electric charge and it can easily travel from the metallic bottom of the car to the ground without any conducting element. The alternative of lying beneath a sheltered and covered non conducting surface might not be entirely risk-free. An average power of the lightning could be of one terawatt which produces high-intensity magnetic field, induced currents and a very high decibel sound. Considering this, a person lying beneath a shelter that is several meters away from the lightning can also be harmed.

** A truck, car or other enclosed metal structure is the safest place to be in a thunderstorm.

Failing that, a ditch, trench or group of shrubs of uniform height is better than nothing. **

agree with the other answer (lie down with head down). the only thing i would add is to be well away from trees or other structures that could collapse. if there is a ditch you can shelter in, i would use that.

be aware that when lightning strikes in your vicinity, ozon will be produced in relatively high concentrations. This is a toxic compound in principle. try to limit breating it in (it should dissipate quickly after)

lie on the ground with your head down