I fly a heck of a lot and have never been upgraded further than Premium Economy.
If you are not travelling alone and do not hold status with the airline, and the flight is not full, forget it. You can ask and be charming if you want but your chances are almost zero.
Even holding FF status does not get you anywhere 95% of the time.
If they are going to upgrade anyone, the upgrades are normally done automatically, and I don't think most check- in crew even have the power to give out upgrades to you for being charming fella. Heck a lot don't even work for the airlines themselves these days!