Originally Posted by VegasGambler

I have never had a problem with this. Get to the gate when the GAs do, and when they are not busy (they are usually not busy when they first arrive) just let them know that you didn't get a chance to pick a premium seat, but from the upgrade list you see that person XXX is likely to get upgraded and ask if they can move you to that seat when that happens. I'm planning on doing this again today as I am stuck in E- but I see that 6A and 6F are probably going to be upgraded.

Once they assign a seat they are not going to move someone so you need to make this request before they start upgrading people.