How to improve my iPhone battery?

I have an iPhone 4S, and within 5 minutes of playing a simple game or an hour of leaving it on standby 20% of the battery is going. How do I improve this? (and I don't want any of that 'turn down your brightness' stuff, it dosn't really do much)

Turn off Wi-Fi, location services, 3g and turn down your brightness when possible.

They have apps specifically to improve your battery, but it requires you to follow instructions such as 'leave your iPhone on for x amount of hours, then unplug it at this time'.

A popular and high-rated app is called Battery Doctor.

It sounds like your battery has run its course. I would make an appt at the apple store and just have them put a new battery in, and everything will be like new again.