Remember back in high school when everyone had their own little clique? Whether it was the football team, the actors, the smart people, or anything else, everyone seemed to gravitate to their own specific group. Well, guess what, as much as you might have hoped that all that was left behind, odds are you'll still see these dynamics in the workplace.
What you need to do, as a new professional, is to try to position yourself outside of these cliques. You don't want to get labeled as "one of the slackers" or something along those lines because of who you associate with. There are many different kinds of cliques in the workplace, and you should familiarize yourself with each of them. Observe what takes place each day for the first couple weeks, and identify what the general office opinions of the different groups are. Ideally, you'll notice that your workplace doesn't have established cliques, and you can proceed on with your career.
Try to make sure you integrate yourself with everyone in the office. You might have your favorites, which is natural. If you can build an environment where everyone is open with their colleagues, your productivity and longevity with the organization will likely grow as well. It won't be easy, but its a great thing to practice as you grow in your career.