"People who should not be tipped
You're probably relieved to read there is someone, somewhere, who's not
expecting cash from you. That doesn't mean you can ignore them, though; it just
means your gift shouldn't be green.
* Teachers. Ask what classroom supplies they need, and supply them. Gifts
of food or a well-deserved day at the spa (perhaps purchased jointly with other
parents) can be thoughtful, as well."