I spent several years behind the front desk of a luxury hotel, and I can tell you when I got asked for an upgrade, the guest never got it. Never. I always found it very annoying.. I would be more apt to give an upgrade or a preferred room to people who were just nice in general, as opposed to those who came in asking for an upgrade and telling me how often they stay in the hotel, or why they are just special and should get something better.
Sorry for a vent, I just always found it very frustrating

, so I guess it still gets my blood flowing even though I got out of that business a few years ago!
Striking up random conversation with a desk agent will go a long way to perhaps getting an upgrade of some sort. It was rare when someone took an interest in where I was from, etc so those people often got the better rooms....