If you have an attorney before your arraignment date, talk with your attorney in advance. The more your attorney understands about your case, the more he/she can help you.
Generally speaking, you should plan on staying at least three hours for your arraignment and in crowded courts you may be required to stay all day, until approximately 4:30 p.m. The courtroom is likely to be crowded and it may be a while before the judge gets to your case. Be early so that you will have enough time to find out where to go and to make sure you do not miss your case being called.