You might be in an environment that is completely unfamiliar. You might not know anyone at this place where you will likely spend around forty hours per week. Realistically, the people you work with probably won't become your best friends, but they can become people that you enjoy talking with, eating lunch with, etc. Some co-workers may not be interested in getting personally involved, but some will be good companions. Dealing with your supervisor can be tricky.
Diplomacy is the name of the game.
If you happen not to like your boss, keep your feelings to yourself. Hopefully, you will enjoy working for him or her and there will be no problems. If you are at your best at all times, you'll have no problems. Make sure you dress properly. On the first day, unless they tell you specifically what you should wear, dress nicely.