How do you compose an image for lightning when you don't know where the lightning is going to strike? If lightning is going off left and right, and all over the place it is not much of a problem because sooner or later you will get it in the right place. But what if that is not the case? What if you only have a strike every now and again? Is there something we can do to place the lightning in the right spot compositionally? How do you set up your framing to maximize your chances of getting the bolt in the right-ish place?
Yes, lightning is unpredictable, but not fully so. We do know where most of the strikes are going to hit for a scene such as this. Lightning tends to strike mostly in or near where the rain "band" is. When you see the rain "band," frame your image close to it, knowing that that is most probably where the strike is going to be.
Look at this image. The rain band is clearly visible just to the right of center. The rain band stops just to the left of the lowest dark clouds on the right. Now we can frame the image loosely based on where that band is. Keep in mind that that band of rain will constantly move. So keep reframing your composition to adjust to this band's movement.
Many people aim the camera too high. Most of the strikes are going to come from the approximate same height as the cell the rain band is from. So there is no need to frame too high. What is said here only applies to storms moving in or moving out. If you are in the thick of things it could strike anywhere. But for these kind of scenarios pictured above your best chance for success is to aim around the rain band, placing the top of your image just above where the rain band starts.
Always follow governmental guidelines for your safety.