Many factors can contribute to noise during Earthworm Action Potentials experiments. Most noise can be reduced or eliminated by turning off overhead fluorescent lighting and moving the earthworm preparation and Bio Amp Cable away from computer monitors, power cables, cellphones, etc.
If using metal dissecting pans, be sure the saline is not creating a connection to the sides of the pan, which will turn the pan into an antenna for room noise. Likewise, if the pins are pushed through the worm and are making contact with the pan, this can create a tremendous amount of noise.
In some cases, you may find that the 50Hz or 60Hz Mains frequency noise cannot be overcome by the above methods; Averaging over a window of several samples (use the Smoothing Channel Calculation) may remove the shifting baseline and allow useable data to be collected. Please see the Instructor's Reference for this exercise for detailed instructions for using scope averaging and other tricks that can help reduce noise.