Photo Courtesy of USA Today
"First, see if any apps have been squirreling away an unusual amount of data by checking the Settings apps in Android and iOS. In the former, tap 'Apps' and then tap the menu button at the top right and select 'Sort by size.' In the latter, tap the left-hand column's 'General' heading and then tap the right-hand column's 'Usage' link. Then tap the listing of any especially hefty app to see if the program itself is dwarfed by whatever data it's saved on the device. Looking at each device's set of installed software in this way can reveal bugs in the apps.
If none of your apps have been on a bit binge, you'll have to try other measures. Deleting unwanted music, videos or photos is tedious but not too painful — every other phone picture seems to come out blurred anyway, while services like iCloud or Google+ should already have all of your pics backed up online. While doing so, remember that in iOS, the Music and Videos apps require you to swipe left across a song or video to see the 'Delete' button."
Read more at USA Today