Originally Posted by Slug
Look at the data usage graph, work out which apps are consuming the most data, and if you need them running then configure them to use less i.e. poll less often for updates, sync at longer intervals etc. If you don't need them then either disable them or log-out of the associated accounts.
Check that "Show wifi usage" isn't enabled in the Data Usage menu, as this will artificially skew the figures.
I am looking at them, but its like general data like facebook and that, But how do you like "end" the programs so it doesnt use background data, like on the iPhone you can double click the home button and then hold the app and then close it from there.