You only get one chance to make a first impression. When you're facing a judge in a courtroom, that could make a difference in the outcome of your case. Dress conservatively, don't chew gum, remove unconventional body piercing elements and cover tattoos if possible. Dress as if you were going to a business meeting. Good grooming is essential.
Before heading to court, make sure your paperwork and all of your evidence is well-organized. Rather than arrive at the courtroom just "on time," get there about 30 minutes early. Late arrivals make a bad impression. Behave in a calm, professional manner -- don't let your emotions get the best of you. When the judge speaks to you, look her in the eye and reply in a respectful tone. Stand up when addressing the court. Get to the point quickly when presenting your facts. If you're on trial, maintain a a calm demeanor during all testimony.