If you have a medical problem, provide documentation from the medical provider. The key here is to not wait until the last minute to request a continuance. The earlier that you request it, the better chance you have of having your requested granted. If it is granted, you will then receive a new trial date in the mail a few weeks later. The key word for Courthouse and Courtroom behavior is respect.
Judges expect it and are entitled to it.
Shorts and t-shirts should not be worn to Court. A highly respected District Court judge in Anne Arundel County routinely sends people home if they appear before him in inappropriate attire. It is not expected that you wear a suit or a dress. The judges simply ask for a clean, neat and respectful appearance. Most District Courts in Maryland have between 2 and 10 Courtrooms in them.