Once you set them up, backups happen automatically, but it’s still possible to have problems with backups. If your iOS device has displayed an error message about backups, or you checked your backup using the technique above and things don’t look right, here’s a few things you can try.
First, in order for backups to work correctly, you have to have at least 100 MB of space free on your iOS device. Personally, I get nervous whenever I fall below about 1 GB of storage available. Using the previously mentioned Manage Storage screen, you can tap on the individual apps in the Documents & Data section, which brings you to a list of documents. By swiping to the right, a Delete button appears, and you can delete individual documents from your device, and therefore they will no longer be backed up (Figure 3). Or, of course, you can simply delete little-used apps or unpopular music.
Figure 3: You can delete individual documents from your iOS device.
You can also choose to exclude all the data from particular apps from backup; refer to the Info screen in Figure 2.