Smile. Nearly everybody around you is a little nervous about starting medical school. It's completely natural to feel apprehensive, but you should also be very excited. One of the best ways to meet people is to look approachable. And one of the best ways to do that is to smile. Remember...you made it to medical school!
Introduce yourself to your classmates. It's important to not wait until people introduce themselves to you. Have an easy way to rattle off the inevitable questions about where you grew up, went to school, what you majored in, etc.
Formulate a basic study plan before the flood of information begins. Consider studying until a certain time each evening before calling it quits on your medical school anatomy studying. You will deal with a huge amount of material in medical school, and managing it well is very important.
Participate in school social events. You will be around your medical school classmates for 4 years. Going to the social events outside of school are a great way to get to know them.
Keep a long term vision of medical school in mind. It's easy to burn yourself out in the first couple of months after starting medical school. Instead of trying to study 8 to 10 hours a day, set realistic goals that will keep your love of medical school alive.
Don't take yourself too seriously. It's ok to make mistakes, especially when you first start medical school. And it's ok to not be the top person in the class. But it is important to keep a good perspective on the whole process.