What should I do at court tomorrow?

Let me explain: I hit a car and drove away and I ended up getting caught. I'm going to court tomorrow and I don't have a lawyer, because I don't think I need one. Also, I don't have any witnesses; is this good or bad? I'm really nervous about this because I've never been to court. I'm 17 and have had my license for less than 6 months. Will this be on my permanent record, and will it affect me when applying for a job/college? Do you think the judge will be tough on me? I'm in a dilemma and I would really appreciate any input!