Which of the following is a common mistake clients make before waxing?

Shaving the area before waxing is indeed a common mistake clients make. The reason this is often inappropriate is that waxing requires a certain hair length for effective removal. When clients shave prior to their waxing appointment, they may cut the hair too short, making it difficult for the wax to grip the hair properly. As a result, clients may experience ineffective hair removal, which can lead to discomfort and irritation.

In contrast, trimming the hair may be acceptable in some situations, as it can enhance the waxing process by ensuring the hairs are at an optimal length. Moisturizing the area before waxing can also hinder the process, as excess oil may prevent the wax from adhering properly to the hair. Additionally, wearing tight clothing is often discouraged post-waxing to avoid irritation but doesn't affect the waxing process itself as shaving does. Thus, shaving is a key error that impacts the effectiveness of the waxing treatment.