These 2 cloud-to-ground (CG) lightning strokes were simple but striking (pun intended). Every such strike actually involves a complex, powerful process. In this photo, note their main channels' close similarities, probably associated with their step leaders' passage through similar winds on their invisible ionizing journeys through the "path of least resistance." Step leaders are invisible ion channels that slither down before each stroke -- fast, but not too fast to be bent by strong winds. When a step leader gets close enough to the ground (or a tree, building, pole, antenna or person attached to the ground), the charge the ground suddenly and repeatedly surges up through the step leader's channel. This forces it to flash and lights up the other leader branches that didn't reach ground. This is the forked lightning you see, completing a powerful circuit between cloud and ground until enough charge builds to cause the next strike sequence. Note the double channel near ground on the strike at right. It is not common (about 5% of all CG strikes I've photographed); but it happens when two step leaders contact the ground charge at the same time.
8 SSW San Jon NM (29 May 97), looking E.