12. Asking about all the beverages on the menu and ordering a Pike Place Roast

It generally takes a Starbucks barista 10 muscles to force a smile, and a few more to stop himself from rolling his eyes as he takes you on a tour of their drink menu. Reward that effort by ordering something less simple.

Via cp24.com

13. Taking too long at the food display and not ordering any

This is a lot similar with the previous item. The idea is that the longer you take to figure out your order, the more you spend at Starbucks. When that does not happen, it makes the barista really unhappy. That also annoys the queue of customers behind you.