Screw a microphone clip onto a microphone stand.
Place a microphone into the microphone clip. Dynamic microphones are commonly used on electric guitars because of their ability to handle the loud sound pressure levels created by guitar amplifiers. Popular microphones for recording guitar amplifiers are the Shure SM 57, Audix i5 and Sennheiser e609.
Plug a microphone cable, also known as a XLR cable, into the microphone.
Plug the other end of the microphone cable into your mixing or recording console.
Place the microphone a few inches away from the grill cloth of the amplifier.
Line up the front of the microphone with the center of one of the speaker cones of the Twin Reverb. The Twin Reverb has two 12-inch speakers.
Move the microphone off axis from the center of the cone so it is pointing at the edge of the speaker.
Move the microphone closer to the speaker for a more direct sound.
Move the microphone further back from the speaker to capture more of the sound of the room that the amplifier is in.
Experiment with microphone placement to capture the sound you are after.