What safety measure should be taken before working on electrical circuits?

Turning off power at the main circuit breaker and verifying de-energization is the most critical safety measure to take before working on electrical circuits. This step ensures that no electrical current is flowing through the system you intend to work on, significantly reducing the risk of electric shock or injury.

Even with insulated tools, wearing protective clothing, or working in daylight, if the power is still on, the risk of accidentally coming into contact with live parts remains high. It's essential to not only turn off the power but also to use a voltage tester or similar device to confirm that the circuit is indeed de-energized before proceeding with any work. This fundamental practice is a cornerstone of electrical safety protocols and is taught to ensure that electricians can work on circuitry without facing the dangers posed by live voltage.