Why is my iphone battery life so awful?

Sometimes ill go out and my battery life will drop from 70% to lets say. 30% when i use it once for like, 2 minutes. Other times it will be regular and just fade away as it should. Also, it will die at 30% sometimes and i have to charge it to make it go back to normal. Btw, i have an iphone 4s that i've had for 1 year and i recently got the ois 7 update. I want to know how to save the battery life because every time i go out to big places- disneyland, football games, etc i can barely use it.

You can try a few things that can help
1) clear recent apps by double-tapping the home button and slide up to end the processes (with iOS 7)
2) keep brightness really low if you don't need it bright
3) Lock it when you're not using it (i.e. Between texts)
4) Leave it off a few nights a week while charging (this helps performance in general)
5) If you need your phone for a long period of time, don't play games, it drains the battery very fast.
Different apps cause your battery to drain quicker, which is most likely causing the inconsistencies.
I believe keeping vibrate and flash off, and keeping your volume low or on silent may also help.
If none of this helps, your battery may just be old. In that case, you can pay to have it replaced, or get a new phone. These methods work for my 2 year old iPhone 4, so unless you've had some water damage to your phone, it should help you, too!

Ik this sounds really weird but it works if you r a male just masterbate and get your spearm and put it in side the charging thing it will clean your z-63816 unless you want to take it to a shop and they will charge about 100 bucks

Iphone 4s = 1432mah battery capacity
don't expect much stamina from battery especially on heavy games and nonstop calls and other battery heavy activities

2, 000mah above is good for everyday use in my opinion
but if you're looking for a phone with the best battery life go for 3, 500mah like the motorola droid maxx

either upgrade your iphone to a phone with better battery capacity, get a spare battery, or buy a powerbank