Karma

Karma's a bitch.
Don't be mean to your barista or else the twenty you think you brought with you will magically turn into a one when you try to pay for your two medium "not too much milk" with two splendas on the bottom cappuccinos.
The barista will be nice and let you come back later.

Learn your lesson.

Dogs and the Order of Things.

Dogs
Why is it that women with those little dogs, (A) always ignore the big "No Dogs Allowed" sign on the door and (B) are always the most obnoxious customers?

The Order of Things
Barista: Hello.
Customer: Hi.
How are you?*
Barista: Fine, how are you?*
Customer: Good. Can I get a small cappuccino?
Please?*
Barista: Yes/Sure/Ok?etc...
(Barista makes cappuccino)
Barista: That will be (insert dollar amount here)
Customer: Ok. (Gives money, barista gives change.) Thank you.
Barista: Thank you, have a good day.
Customer: You too/Thanks.

The above should be how a normal transaction goes. It's not.
Please see below.

Barista: Hello.
Customer: Small Cappuccino.
Barista: Ok/Yes/Sure/Etc....
(Barista makes drink)
Barista: That will be (insert dollar amount here).
(Customer shoves money in barista's hand, barista gives change.)
Barista: Thank you.
(Customer is already gone.)

*optional