How should I act when I meet my friend's friend?

Pretty soon I am going to be meeting up with my friend (who is a relatively new but very good friend of mine) and a guy who he has known (and been friends with) for a very long time. I have never met this guy before and I want to prevent any awkwardness. What can I do and how should I act? I am generally a quiet and reserved kind of guy, but I am slightly worried that my personality might just make the situation a lot more awkward. Please help me.