Final answer:
The shampoo cape should be securely fastened around the client's neck and cover them from the neck down to protect their clothes during the shampooing process.
Step-by-step explanation:
The proper position for the shampoo cape while shampooing a client's hair is to ensure that the cape is securely fastened around the client's neck to prevent water and shampoo from dripping onto their clothes. The cape should cover the client fully from the neck down.
When applying shampoo, the hair should be thoroughly wetted, the shampoo evenly distributed throughout the scalp and hair, and massaged gently before being rinsed out, followed by the application of hair conditioner if desired. It's important for the comfort and satisfaction of the client that the cape is also adjusted comfortably to prevent any pulling or discomfort around the neck area.