Here are the low-hanging fruit for reducing cellular data usage on iOS 7 iPhone & iPad devices: 1) Settings - Wi-Fi - On
- Join trusted WiFi networks where possible. (However, you likely want to keep "Ask to Join Networks" off so as not be bothered by general join requests.)
2) Settings - iTunes & App Store - Use Cellular Data - Off
3) Avoid steaming video and audio via websites or dedicated applications like YouTube or Pandora while on a cellular connection.
4) Settings - Cellular
- Limit what Apps have access to data over cellular. Choose wisely.
More detail found here: