Appearance should not matter in life. Appearance certainly should not matter in court in the justice system but it does. You should dress conservatively as though going to a conservative religious service. The goal is not to look stylish but to show respect to the court. You do not need to buy a new suit or dress but you should dress up. Do not wear a lot of jewelry or expensive items.
In family court, try and avoid bringing young children. Bringing support is a good thing but be careful about significant others, particularly if no it involves an ex. You generally can not bring a friend or relative with you while negotiating or when in front of the judge.
Make sure to arrive Early for court to find parking and to wait in line for a metal detector. Expect to be waiting in court for a while.