If you’re backing up your iPhone, iPad, or iPod touch to iCloud, you may find that the amount of data you have on the device exceeds the amount of iCloud space you get for free (5GB). One option in this case is to purchase more storage space — it’s not too expensive.
Another option is to cut down on the amount of data you’re backing up. Go to Settings, scroll down to iCloud Settings, then scroll down to Storage & Backup. Select this, then select Manage Storage. Choose your device under Backups. Now, under Backup Options you can choose the data/apps that will be backed up. If something doesn’t need to be backed up to iCloud, turn it off.
In this way, you can customize what is backed up and optimize your use of the free space you are allotted in iCloud.