Simply call the hotel and ask for the GM's name and email address. I would be surprised if you come across a property that won't give you that information. You could even just simply leave a voicemail. Once you have that, just simply state your request, be polite and 9/10 times if the upgrade is available, you'll get it. Just remember to [I]ask[I] for the upgrade and not tell them to upgrade you just because you're Joe Platinum. Again if an upgrade is available, I would be shocked if a property doesn't do it. If the room type you're requesting isn't available on Marriott.com for the dates you're looking for, there is a very high chance that room type is sold out and they won't be able to upgrade you.