Back in the days of the Ice Age, when I was flying CO, I had just become Gold for the first time and was getting upgrades to First on every flight. (This was way back when Gold was the top Elite level in OnePass... I think it was Limestone, Quartz, and Gold

)
I had to take a quick trip to AUS to meet someone at the airport (old AUS Municipal Airport). Anyway, our meeting was not long and I wanted to take an earlier flight back. In those days, there was no way for a regular passenger to see the availability of First Class. You just put your upgrades in the hands of the Gate Agents. So I called CO to get placed on the earlier flight. I asked if there was any room in First still open, and the agent said yes, there were still a couple of seats, but I had to speak to the Gate agent for an upgrade.
There were two gate agents. One was having a dispute with a customer. I went to the other, with whom I had dealt several times. I gave to the agent my paper ticket with my Gold Elite ID card, which we were asked to show in those days. I explained that I had been rebooked on the earlier flight and needed to be reticketed. I then asked in a friendly way to be placed on the list for First. About 10 minutes later, I was called to the podium and handed a boarding pass in First. The other passenger had been demanding with DYKWIA to be put in First, to no avail. After I boarded and sat in First, which was full, the other passenger boarded and glared at me as he walked back into Economy.
The point is, I was friendly and non-demanding, sat in First, and had a good flight.
I was flying on an inexpensive fare and have no idea where I belonged on the Upgrade standby list. It was in the hands of the Agents. I may have been put in First ahead of the guy who was at the counter first on a higher fare. I did not know.
There is more transparency today with the waiting order for upgrades so Gate Agents are under more scrutiny.