iPhone 5 Battery draining fast, help!

Hey

I know a lot of people post these but I really would appreciate help. I've noticed that my iPhone 5 battery is draining really fast, when I first got it as factory settings applied there was good battery life, but when I restored it to a backup, I've been noticing the battery drains really fast, I don't know if it's cause of the back up or not, I mean it shouldn't be right? I've heard you can restore to factory settings then restore as back up again, I'm wondering will that work? I've also heard that you should drain your battery to under 20 and then do a full recharge, I did that yesterday, I drained untill it died then full charged over the night to 100%. It didn't seem to help, I don't know if you should do this many times or not? And some say I should charge it a lot, I do charge it a lot but it seems like the battery was better when I didn't charge it as much, I really don't know and I would really appreciate help and information. Feel free to add anything extra that you wanna say, oh and also I did a test, I put radio on, on my iPhone 3GS and my iPhone 5, and when the battery had drained 2% on the iPhone 5, it hadn't drained anything on the 3GS.

Thanks

PS. Yes I close apps running in backgrounds and all that.