Besides the tic'ing, i'll also watch the line speed. This is half visual, half 'feel'. You 'sense' the line pause, diffent from the tic on a rock, and set the hook. The really tough ones are the ones that come from behind, pick up the bait and swim with it for a few seconds. The lead still tics, and unless your sharp hook finds a good place, it'll be spit out and you never know it happened... This is where you hope the yarn gets tangle in the teeth, or that he really likes the taste or texture of your bait and holds on a little longer.
I apply this to drifting a (usually weighted) fly and even to spoon\spinner fishing.