This is kind of small but here it is: there are certain keys on the Samsung sch-u740 one of them is the pound key if you hold that down it turns the phone to vibrate and when it's in vibrate and you hold the pound key once more it turns it back to normal mode. Also, if you have speed dials and you hold the # of the speed dial it calls them.  These are my tips.  From, Chris Chiaravalli