Shooting lightning with Nikon D3100?

I have been trying to capture lightning because of all the storms here letely, I was wondering if there was an optimal Iso setting and shutter speed, I have been going at 1/320 and a very high iso, I expect I don't need my iso high because of the light from the lightning. I also think my shutter speed might be too high. Any suggestions would be great!

Lightning is very bright and happens quickly.

Start with these settings and fine tune:
ISO: 200

Shutter speed: use bulb mode. Keep shutter open until flash of lightning, then close shutter. This only works for night shots of lightning. If you don't get a strike within 1 minute, close shutter and try again. Using a shutter speed of 1/320, chances are you will never get a photo of lightning unless you are incredibly lucky. There's no way you react that fast.

Aperture: f/13. Adjust this to your tastes.

White balance: daylight.

While a tripod is handy, you can hand hold the camera close to your chest unless the foreground is lit.