Why does my iPhone 4s lose power so quickly?

I always close my apps when I'm not using them. I don't use my phone excessively. I don't understand why it's dying so fast? Is there something I can do to conserve power?

You may have apps running in the background and don't realize it. Usually things like the Weather Channel/Weather Bug or Twitter. Those are apps that are constantly running. Or if you don't log out of apps like Pandora, Facebook or Instagram. Even when they're closed, the fact that you're still logged in makes it run.

With me, it's part of the above reason, as well as just my reception area. Where I live, there's plenty of reception, but right down the road a few blocks to school and it's a dead zone. Also, when I'm at work or at clinicals (a radiology office and a hospital) the reception isn't great because they usually try to block part of it.

Brightness too high

Yes. Turn off data when you don't need it, turn off Wi-Fi when you don't need it, go into Airplane mode, lower brightness, close background apps d(ouble clicking the home button and tapping "x" on the corner of every app), setting your screen timeout to the shortest length possible, turning off the GPS, turning off Bluetooth, turning off phone vibration, putting your phone in sleep/standby mode when you're not using it, and I also recommend installing a power management app. There are a lot of them on the app store.

Why have the iPhone if you turn All the features off just to save the battery?