iOS: Some apps are greedy and can eat up all your mobile data. Luckily, iOS 7 lets you restrict data usage for specific apps to Wi-Fi only.
This handy tip comes to us via Cult of Mac. To adjust the data settings, all you have to do is go to Settings then Cellular. You'll have the options to turn off all cellular data, disable 3G, or turn off data roaming. Swipe to the bottom to see the list of iOS apps using mobile data -- and how much data they use -- and toggle the switch to force apps to only use Wi-Fi.