Which of the following represents a proper practice before working on an electrical panel?

De-energizing the system is a critical step before working on an electrical panel because it significantly reduces the risk of electrocution and other electrical hazards. When the system is energized, any accidental contact with live components can lead to serious injuries or even fatal accidents. By ensuring that the system is de-energized, you not only protect yourself but also create a safer working environment for everyone involved.

In contrast, while reviewing installation manuals, organizing tools, and checking local codes are all important parts of the preparation process, they do not directly address the immediate safety concerns associated with working on live electrical components. Reviewing manuals helps you understand the specific equipment you are handling, organizing tools ensures efficiency during work, and checking local codes ensures compliance with regulations, but none of these actions can replace the fundamental necessity of ensuring that the electrical system is de-energized first. Prioritizing safety through de-energization is the foundational practice that underlies all subsequent activities when working with electrical equipment.