Upgrades are very few and far between. I don't know that there are any tricks. We've done everything that you would think would get an upgrade from outright requesting them, to having notes made on our reservation when we were celebrating a birthday, to being extra chatty with the CM's at check-in.
The only time we've gotten an upgrade was at AKL when we booked a standard, and they were apparently overbooked and put us in a savannah view. Truly though, upgrades are very rare and I believe it is just luck of the draw. When we did get that upgrade, we were not there for a special occassion, hadn't asked for one, or anything like that. I also think if you ask for one, you shoot yourself in the foot and are looked at as just another guest looking for something extra for nothing. I tried that once, and really felt foolish afterward.