EXPRESSION
The look on your face tells customers a lot about your attitude and feelings. Your mouth and eyes are the most expressive.

SMILE!
It may be the most important thing you do all day.
It is impossible to look fed up or look disinterested when you smile.

SMILE!
You could make a customer's day brighter.
There's little point in saying something like: "Have a nice day" if your expression tells the customer that you really couldn't care whether they have a good day or not.

Use your eyes. Look at customers. Catch their eye occasionally. There's no need to stare or gaze at them! Just show that you are paying them attention.