Final answer:
Electrodes for Lead #1 in an ECG should be placed on the right arm and left arm to measure the voltage difference between these points as part of the standard 12-lead ECG setup.
Step-by-step explanation:
While prepping a patient for an ECG, the electrodes for Lead #1 should be placed on the right arm and left arm. This lead measures the voltage difference between the right arm electrode and the left arm electrode. In the standard 12-lead ECG setup, a total of four electrodes are placed on the limbs, and six electrodes are placed on the chest. The complex electrical signals of the heart are recorded through these placements, providing a detailed analysis of heart function.