The trick is to balance your bobber with your weight/hook. First use the smallest bobber you can get away with, secondly your weight and hook should almost pull the bobber under the water. What I mean is that the bobber should be almost completely submerged. If you are minnow fishing, you may have to lighten up on the weight so the minnow cant pull the cork under. Rigged this way, if the bite is up, the cork "POPS" up and if the bite has any downward motion at all, the bobber will sink.