Take a few inspiration pictures with you. Be aware that not all styles work on all hair. Fine hair doesn’t style the same way that thick does and some styles require extensions. Be assertive about what you like and what you don’t. This is not the time to be a shy people pleaser. Do not leave the appointment until you are 100% satisfied with their work.
Try to show inspo pics with similar coloring to yourself (goes more for makeup) and let them know if you plan on dyeing your hair for the wedding. That way your mua will be able to pick colors that flatter you and don't clash with your undertones or anything