How does the old man manage his lines in a way that makes him different to the other fisherman?

The old man in the story does not often have much luck any more with his methods of fishing. He keeps his lines extremely straight, letting them fall straight down into the water and ensuring that there is some bait for the fish at each separate level, no matter at what depth the fish should be. The old man fishes with what he calls "precision": he wants to know exactly where the fish will be when they bite. The other fishermen do not have such a preoccupation with this—they simply allow their lines to float with the current, such that the fish might take a bait that is at sixty fathoms deep when the fisherman think the bait is far deeper in the water. It doesn't matter to them; they fish in a way that relies upon chance, whereas the old man wants to know exactly which fish he is targeting and where they are. He keeps his lines still and waits, rather than moving and trailing his lines through the water.