NEW YORK — Many of the nation's service workers — from waiters to doormen, barbers and manicurists — make do because of tips. So it's especially important to remember them at the holidays.

Unfortunately, there's no simple formula for holiday gratuities, because what you give and when you give it varies by geography as well as your temperament and your budget.

"In our world, we view the holiday season as a way of saying, 'I appreciate you,' " said etiquette expert Peter Post. "That's a nice tradition."

At the same time, he said, "this isn't a command performance that should force you to go into debt. You should give a gift within your means."

There are, of course, two basic ways to reward those who have provided good service through the year — cash or presents.

Cash or gift certificates may seem somewhat impersonal, but they're appreciated by people who rely on tips rather than on salary for their livings. Presents, especially those that are homemade, can be more appropriate for salaried professionals such as teachers or nursing home workers.

Post, a great-grandson of the late etiquette maven Emily Post and a director at The Emily Post Institute in Burlington, Vt., said one of the best ways to find out what the norms are in your community is to ask around.

"Ask your friends and neighbors," Post said. "They'll generally be more than happy to talk about local customs."

If you're uncertain how much to tip a particular person, such as your hairdresser, "ask the shop owner what she would recommend," he said.

As an example of tipping a service worker, Post suggest that if a personal trainer charges $50 an hour, you should tip the trainer $50 for the holidays.

But Post said that this isn't mandatory.

"There's nothing that says you can't give your trainer a $25 gift," he said. "It's always an individual decision."

Those who decide on a present should put a bit of thought into "selecting something that has to do with them," he added. In the case of the personal trainer, for example, that could be a coffee table book about a sport the trainer follows.

Consumer finance expert Nancy Dunnan points out that there are regional differences to how people tip.

Cash and gift certificates tend to be favored on the coasts, she said, while many who live in Central States prefer giving gifts, "often something they've made like cookies, knit scarves or things like that."

On the gift-giving side, Dunnan believes parents should involve children in making or selecting gifts, especially for their teachers and caregivers.

"This is a wonderful opportunity for parents to bring out the creativity in their children and to show them there's something beyond money to the holidays," she said.

Post, who has written a number of etiquette books, including "Essential Manners for Couples," said families can be creative with gift certificates, too.

"I like them because it's not just that cold, hard cash that could be used for tomorrow's groceries," he said. He favors gift certificates for a restaurant or coffee shop, bookstore or movie theater.

Families should be aware that some workers are not allowed to accept cash even at the holidays, Post said.

According to federal regulations, mail carriers can't accept cash but may accept gifts of up to $20. Some schools prohibit teachers from accepting cash, and similar rules can apply to doctors, nurses and other hospital workers.

"Teachers are especially tricky, almost a special category," Post said. That's because parents sometimes try to one-up each other to promote their own children, much to the embarrassment of the teacher.

He suggests that one way around this is for parents to pool their money for a single gift.

"It removes the issue of competition among parents, even if it's inadvertent," Post said.