On my business trip from Kuala Lumpur to Hong Kong, I am luckily upgraded to First Class from Business Class. Just want to share how I got upgraded as it was not done by the airline.
Sometimes, when the airline changes aircraft, when the original aircraft does not have first class and the new aircraft does, imagine nobody would have bought the first class seat. I had seen it twice already that during online check-in time frame (48 hours before departure for many airlines), they just opened up the first class seats for business class passengers to assign. My usual practice is even business class seat, I tend to block off rows more upfront and sometimes this gives me first class seats. Of course, this is a bit of luck too. But do not worry if the “seat configuration” is a bit odd when you block business class seats. I have upgraded myself twice this way.
Hope you enjoy my tips! Cheers!