Final answer:
Before beginning each service, an esthetician should wash their hands with soap and warm water to maintain proper hygiene and prevent the spread of infections.
Step-by-step explanation:
The step an esthetician should perform before beginning each service is B. Wash hands with soap and warm water. Handwashing is a critical practice in maintaining hygiene and preventing the spread of infections in a clinical or salon setting. Proper handwashing involves using soap and warm running water, and focusing on areas that are common for germs to reside such as the thumb, wrist, between the fingers, and under the fingernails. These measures help to protect both the client and the esthetician by reducing the potential transfer of microorganisms.