So true story, my girlfriend and I had spent the weekend on vacation, and as we were driving back it started raining. The further we went, the more intense the storm became. She suggested we get pictures of the lightning strikes. Which rocks, except for one thing, I have never taken lightning pictures. Didn't even have a clue, just a hypothesis in my head. So luckily we were in a spot that had cell service. I checked google, got my instructions and went for it. Safety is totally a concern when taking these kinds of pictures. Lightning is something you kinda don't want to f*ck around with.
I would say the most important thing behind safety, is being patient. It took about a hour. It is very hard to time lightning strikes and depending on how long your exposures are, you will get a few with zero. The area I was in was extremely dark, so my camera settings were base iso - 64, 30 seconds exposures at F5. I was using my Nikon D810 and the amazing Nikon 14-24. Truly beautiful combo. Of course I had it sitting on top of my tripod.
Hope this helps and have fun shooting :)