How to see if your iphone is charging?

I just got the new iPhone 5.It had about 80% battery power when I got it and several hours later, it is in the red zone. I tried charging it with the enclosed wall charger but can't tell if it is charging or not. How can I tell and what can I do to preserve battery as long as possible?

You have to see if there's a lightning bolt next to the battery icon (if you have ios 7). The lightning is on the battery icon (if you have ios 6) p.s. The battery icon is on your upper right corner