Despite the naysayers, I can assure you (speaking from the airline perspective) that it absolutely doesn't hurt.

I am managing a flight oversold in Y at LGW tomorrow morning due to an aircraft swap and all status pax/VIPs have already been pre-upgraded. We will need to pick approx. 7-10 additional pax to upgrade during the checkin process. I assure you that passengers wearing jackets and/or ties stand significantly higher chances of snagging the upgrade than someone in a T-shirt, shorts and baseball cap. It also helps if you can make the checkin agent smile by cracking a joke or just basically empathising with them. Nobody wants to upgrade the sloppy grouch who argues.

I personally tend to be partial towards retired couples traveling together as they invariably enjoy the experience and are very low maintenance for the crew. Having a title like "Doctor" or "Reverend" in front of your name is another good indicator of someone who can fit in. Of course, others have different styles and preferences.