It is important that you know your options for backing up your device. If you are running iOS5; iCloud and iTunes can back up your data on iPhone, iPad, or iPod touch. The back up includes purchased music, TV shows, apps, and books, photos, videos, app data, messages, ringtones etc.
Back Up With iCloud
Apple gives you 5GB of free space to store your own data like photos, messages and ringtones. But you get unlimited free storage for purchased music, TV shows, apps, and books). To enable iCloud back up, simply tap Settings > iCloud > Backup & Storage.
After you turn on this setting, your iPad/iPhone/iPod Touch will back up daily, automatically as long as your device is on a Wi-Fi network, connected to a power source, and in the locked screen mode. You may also initiate back up manually by tapping Settings > iCloud > Storage & Backup and then tap Back Up Now.
If you need more iCloud storage, you can purchase additional iCloud storage. To learn more, please visit: http://support.apple.com/kb/HT4874
Back Up Through iTunes
The other backup option you have is backing up with iTunes. iTunes can create a backup file on your computer, This option can be better for you if you want to back up without using a Wi-Fi connection. If your iCloud backup is turned off, Syncing with iTunes will create backups of your iOS device. You can also back up by right-clicking (Control-click) the iOS device in iTunes under Devices and select Back Up. Please note that iTunes will not back up automatically if you are using iCloud.
The iTunes back up files on your computer are located:
Mac: ~/Library/Application Support/MobileSync/Backup/
Windows XP: \Documents and Settings\(username)\Application Data\Apple Computer\MobileSync\Backup\
Windows Vista and Windows 7: \Users\(username)\AppData\Roaming\Apple Computer\MobileSync\Backup\
How to delete a backup created by iTunes
You can delete your iTunes backup by opening iTunes Preferences ( Windows: Choose Edit > Preferences; Mac: Choose iTunes > Preferences), then click devices where you can locate the backup for the iOS device you want to delete and click Delete Backup.