Don't be the customer who orders a drink and then proceeds to make the barista wait 5 minutes for you to decide what to get. You're not in college anymore, buddy.
Tip: 5-10% of your drink order
Smile and wave at the barista, even if you're secretly judging them for their hairdo. It's not that hard.
Tip: $1-2
Pay for your drink with exact change, no matter how much you've been drinking.
Tip: 10-15% of your drink order