I like to use my computer’s microphone and audio output when I want to record my voice in the Audio Hacker, but you can also connect an electret microphone using a simple circuit. An electret microphone is handy for applications where you don’t want a computer. Electret microphones have polarity, so make sure you connect the positive/negative leads correctly in the circuit.
Since the output of the microphone is very weak, turn up the preamp gain on the Audio Hacker shield until you are happy with the level (probably all the way up!). The preamp provides up to 100X gain. Connect the microphone’s positive lead to one of the input pads. It doesn’t matter if you pick ‘L’ or ‘R’, or connect the microphone to both.
Another approach is to use this handy microphone breakout board from Sparkfun. It includes a 100X amp so you don’t need to amplify its signal with the Audio Hacker preamp.