^ Put your shutter speed to "BULB" mode. it means you can hold the shutter open by holding the shutter release button down. After the lighting hits.. just release the shutter button. If you try and take the picture right when the lightning hits, you might get it, but most likely not. If anything, you'll just get the return stroke.. You can tell whether or not you got the initial stroke by the picture.. those two you see that were posted are of an initial lightning strike, otherwise you wouldn't see all those "feelers" on coming off the bolt. secondary or return strikes don't have feelers.

It helps a lot if you have a remote shuter release so you're not shaking the camera. Just take the pics with a dark background so you can hold that shutter open for a long time without over exposing the film.