Arrgh! I had typed an in-depth answer, and then lost it. Oh well.
In short, many of these battery apps will make things worse, and make your phone less stable, and more prone to crashing. There are some apps that work by shutting off data, and all the radios except cellular, and only turn them back on every now and then (say, once an hour). They work, but at the expense of turning your smart phone into a dumb phone 59 minutes out of every hour. If someone sends me an email, I'd like to get it right away, not when the software decides to turn data back on.
You might find this thread useful:
http://forums.androidcentral.com/samsung-galaxy-s3/278622-battery-life-tips-myths.html
What kind of battery life are you getting? If it's really bad, you may have a software issue that can be addressed. If you just think it should be a bit longer, the thread above might help, or a larger battery. Give us some more details and we can provide more specific answers.