I must admit to having been bumped up quite a few times during long haul travel.
So far BA and Air Canada have been the best airlines in the freeby upgrade, 1 thing that does work in my favour is being 6ft 9inches tall
i always check-in seperately from my mum and dad i wait at least 1/2 an hour after they have done so, i dress semi casual (a good pair of trousers and casual shirt have never been out of fashion).
I always make the point of finding out the check-in persons name and calling them by it, asking them how they are etc etc. Then i always ask for a seat with extra legroom, 1 by an exit or near the partition, because of my freakish height. too prove the height i say i am, i always carry a Doctors letter saying that im 6ft9" tall and weigh in at ***lbs and a normal seat would be uncomfortable.
1 airline that didnt upgrade me was Cathay Pacific LHR to HKG, but i got a entire row of seats to myself by an exit which was nice, but i didnt need it in the end (this was pre 9/11) i asked for a flight deck visit, which got granted, i was allowed to stay up there for 5 hours which also included the approach and landing into Kai Tak on the Checker board approach.
I kept asking the Capt and FO if they wanted me to leave, but they said no stay up front, nice to have somebody to talk too etc etc, got an indepth lesson on the 744's systems incl demonstrations of how the FMC and auto throttle works.