Having notifications from Facebook, Twitter and your e-mail "pushed" to you as soon as they arrive is convenient, but it eats up data. Unless you absolutely need notifications immediately, make sure that any application with a "Refresh" setting is switched to "Manual" (instead of being on a timer), and turn off push notifications for your e-mail app. Finally, check to see that auto-sync (usually found on e-mail clients and calendars) is disabled. For heavy users, these tweaks can reduce consumption by hundreds of megabytes a month. Other tips: Switch to Wi-Fi before refreshing apps that require data, as well as before updating your app library, and at home leave the phone connected to a Wi-Fi network.