How do I prevent my new iphone 4 from getting hot in the first place?

I got a new iPhone 4 for Christmas. It is constantly overheating and getting insanely hot when charging. My battery life is suffering, it takes hours to charge and loses battery life very quickly. How can I prevent my device from getting hot in the first place? I use it in a room temperature environment and only have about 2 apps running at one time.