If you want to know peoples gamertags look on their profiles. If you want to be friends with them leave a message on their profiles. Mine isn't on mine because i don't want to be friends with random people. Also, why haven't you told us your gamertag?
what i would like to know is what makes you think every person plays on xbox live? and like what master said if you wanna know peoples gamer tags then just look on their profiles and if they dont have something listed try asking them
