From what I remember doing this many years ago: Camera on tripod. Point to where lightning is frequently seen. Focus on infinity. Set ISO low to allow slow shutter speed. Small aperture to allow large depth of field and slow shutter speed. Trip the shutter and hope for the best. It's good if you can keep the shutter open as long as possible to have it open when the lightning strikes. If lightning doesn't strike then trip the shutter again as soon as it closes. This is a hit-and-miss method, but the best I can think of if you don't use electronic traps.
I got a nice picture of lightning this way years ago, but on a Pentax camera so I can't show it here.