Carry local cash in several places on your body (just in case of pickpockets) Some debit cards will cancel the processing fees if you use a local teller machine.
Write down your hotel room key mixed up on the key jacket in case you lose it.
Try not to do shop talk loudly (I know it's difficult) but there's lots of people listen that you haven't interacted with.
Drink lots of water on the layover you'll be dehydrated and tired, but then get a few brews before dinner if that's your gig.
Enjoy the sights if your layover time allows it.
Second the Do Not Disturb sign !
Have lots of laughs and fun....