Hello lesmore49,
I agree with Rondec, what you need are good techniques, time and patience.
Here are a couple I took during a recent, very severe thunderstorm. Pentax K10D, Miranda 24mm f/2.8, ISO 100, tripod, cable release. Aperture Priority (Av) mode, f/6.7, exposure times 4 to 6 seconds. I also played with -1/2 to -1.0 Ev, but this depends on your taste on foreground detail or all-black sky and landscape. With no Ev, you'll get more foreground detail and a lighter overall photo, but the lightning will lack contrast.
Set up in a safe place (I should take my own advice, was under a tall tree!) like a wooden shelter or overhang; this is mainly to keep the lens dry, water droplets won't enhance the photos at all. Just keep clicking every time the the previous photo shows up on the LCD screen. One "Strike" photo out of 20-30 frames would be considered a good ratio. Some form of rain covering, plastic bag or camera hood is nice, there are many available from eBay or you can rig one up with plastic bags and rubber bands. A skylight, CPL or ND filter is very useful, chances are you'll have to wipe the lens eventually. It's better to wipe a filter than the front optic of a lens. Lens hood is a must, but won't stop blowing rain.
The longer the shutter speed, the more chances you'll catch a flash, all things being equal. So, in my case, f/8.0 ran about 8 seconds in Av. Stopping down to f/11.0 would require a 16 second shutter speed (one full stop, lets in 1/2 the light, so the shutter speed doubles to create the same exposure. Half the light, twice the time), f/16 would run 32.0 seconds, and so on. There can be problems with very small (high f-number) apertures, to avoid this a ND # 8 or # 9 will darken the scene 3 full stops. In my case the 'crash-boom!'s were only about a minute apart at the peak, I just kept clicking.
Good luck and tell your friend to stay safe!
Ron