My rule of thumb on those machines is: If nobody is there, no tip. If someone is there doing something for me, at any level, I ask them if they personally get the tips. If they say yes, I leave a commensurate amount depending on what I’m buying or where I’m at. Other rules of thumb: Bartenders at my regular places get tipped more. As said previously, “how quickly do you want your next beer.” It’s nice showing up on a busy Friday night and they make your drink and hand to you and leave other people puzzled who have been standing there 5 mins or more. Restaraunts/Bars where you hang out for a while? Tip based on the expected turn rates and average tabs for the table. So if you sit at a table for 3 hours and prevented the waitress from serving three separate groups in that time, don’t be a dick and tip her maybe 3x. Sometimes even giving a $20 upfront and telling them you’ll be hanging out a while can go a long way.