You can run several apps on your Android phone with multi tasking. So, you can flick through your favourite apps like Twitter, Facebook & news all at the same time. With multi tasking the apps you have opened continue to run in the background and use data off your smartphone plan.
To keep an eye on your data usage here are a few handy hints:
Download an app called taskKiller, which lets you quit applications running in the background.
A helpful tool for managing your spend is Vodafone's My Account. You can track how much data you are using and how much you have spent, and it's FREE!
Check how much data and battery life different apps are using. There is a selection of apps available, just search for 'track mobile usage apps' and select your preferred app.
Switch to WiFi: When you're in a WiFi hotspot i.e. at home. You won't use any of your mobile data. Go into your phone settings and turn WiFi on.
Change your settings: So that the content of your apps will not refresh constantly. To do this go to app settings and change the refresh time to be less frequent, 1 hour or 3 hours.