Quick as a Wink ;-)
To keep it simple the trick is to keep a long exposure. But that would work in low-light conditions so adjust the shutter accordingly. You cannot predict when the next lightning will strike and its so quick that you can’t keep your hand on the shutter and coincide your click with it. But what happens with the long exposure (10-30 sec or even in bulb mode) is that the shutter is open long enough to catch one if it strikes again in that 20-30 seconds. If you are lucky you can get multiple lightning strikes in that 1 exposure.
So go out, take some shots BUT REMEMBER to keep yourself safe, needless to say thunder storms and lightning can be very dangerous. As you can see I kept myself safe by not staying out for too long.. hence not too many of them.