It very much depends on the type of Bridal Boutique and the position you’re aiming for, but ideally you should be qualified as a sales consultant with at least two years of experience. It is unlikely to be asked for customer service qualifications, as the skills can be proven easily and are incorporated in sales training. If the position is floor sales consultant with permanent product-related contact with customers, a junior sales consultant qualification should be enough. You should have had sales training courses for at least one year, but it again depends on the shop. A strong sense of aesthetics and fashion knowledge might also need to be proven, mostly in practice rather than on paper. In the case of a managerial or executive position though, further qualifications will be required such as senior sales executive or even a business degree.
Sales experience, knowledge of designers, knowledge of what would look nice on certain body types. When my daughter got married, our sales consultant had these skills and was so helpful.