Many EEG experiments are done using 21 electrode helmets to gain better localization resolution. In our case, this will not be necessary. Since the secondary motor area generates the readiness potential, the strongest RP signal is found immediately over that region, contralateral to the side of the body performing the task. In our case, the right hand is used, so our two electrode EEG headband will be positioned over C3 and Cz, according to the 10-20 chart.
The RP has an amplitude of 1/10th that of an alpha wave, so there will be no way for a human to look at a recording and see the RP building before a wrist flex. We're hunting for a tiny signal in a lot of noise, so the RP will only be visible after a ton of averaging.
I've got the device built: It's just an Arduino with the Backyard Brains Heart/Brain Shield and the Muscle Shield stacked on top. Analog data from both shields is converted to digital by the Arduino and sent to the computer by USB, where I'm using the free Backyard Brains Spike Recorder software to visualize and record both channels. There are a lot of issues with RF noise, so I've had to look around for a good location away from fluorescent lights and power cables. Perhaps an anti-static wristband would be useful.
I'm using MATLAB to process the recording, recognize the muscle spikes, and average the EEG signals before and after the onset of the action. This is the tricky part for me, since I have very little experience programming in MATLAB.