From the Backup & restore section, ensure the appropriate account is selected from the "Backup account" field then tap the following switches toturn on or off :
Existing backups are deleted from Google's servers if you disable data back up.
Back up my data
Personal data such as Wi-Fi passwords, browser bookmarks, user dictionary, a list of installed Market apps and other customized settings are backed up to Google's servers.
Data and settings are restored to apps utilizing the backup service upon re-installation.