1. Wait for lighting strike.
2. Press shutter
3. &*&$#@#$! your timing
1. Set camera on tripod.
2. Select a mid to small aperture e.g. f/8 ~ f/11
3. If your camera has B mode, open shutter and wait for lighting strike.
4. When that happens, close shutter.
If no B mode, use something like 4s - 8s in step 3, and hope that lighting will strike within that period. If you observe enough, you will find that the strikes might be at regular intervals, making it easier to predict.
Ideally shoot lightning at night or near sunset/sunrise. Use a mid apeture of around f8-f16 and a slow ISO setting to give you the maximum shutter time permissable.
If you can see lightning then it can strike you!
This is an often overlooked fact, lightning strikes have been recorded up to about a 30 radius around storms proper. Just because you arent' under cloud cover doesnt' mean you aren't vunerable.
Where possible shoot from indoors, or in a car. While not completely shielding you from lightning cars and houses offer some protection from strikes.
Finally learn all you can about lightning and it's behaviour. From what I've read recently there's been considerable advances in the past decade in the understanding of lightning and in particular its discharge mechanisms, including the randomness of strikes and how little difference a 6 foot human makes relative to the normal 1000-40,000 thousand foot path of a lightning bolt.