1. Tap Settings, General, Reset, Reset All Settings. Note, no data or media will be deleted.
2. After the phone resets the original factory or default settings, you will be asked to setup your phone including Location Setting, Wi-Fi, Siri as well as accept the License Agreement Terms.
I did notice when Siri started working that the Siri screen with all the options briefly flashed. This might have caused my iPhone 4s to lock up when The Siri program crashed.