We have quite a few questions on tipping in the USA, but looking through I can't seem to spot one that covers this.
When in the USA, if you are somewhere where drinks are free but served to you, is it expected to tip the person pouring / bringing the drink, and if so, how much?
Additionally, does it vary by location / setting? For example, might an airport / hotel lounge differ from an all-inclusive hotel / resort?
(I'm currently in an airline lounge at a US airport, and was given some vouchers for free drinks when I entered, which are given to the barstaff in exchange for drinks. Some people seem to give a tip, some not. A few weeks ago I was in a hotel lounge which had free drinks for an hour in the evening, with a member of staff removing beers from the fridge and opening them for you, but I was the only one there then so didn't have anyone to copy....)