by madhu bheemagani.
Before Upgrading you must check below requirements
Before upgrading what all the plug-ins available in Moodle 1.9, you have to cross check once in upgraded version plug-ins available or not in Moodle 2.2 package, if not there you have to put in respective plugins folder.
You have to be more careful if you have installed additional plug-ins or customized the code.