Here’s a tip: It’s not easy

You get decent service, you leave a tip, right?

It’s not always that easy. One consequence of the ballooning service economy is that new tipping opportunities are springing up everywhere.

How much to give the guy at Starbucks, the concierge, the bathroom attendant? What to do if a restaurant quietly tacks on a “service charge,” as more upscale places are doing? At Duvet, for instance, a pricey New York nightspot, tables are charged a mandatory 20 percent tip no matter what.

Other eateries, along with a new waiters’ group called fairtip.org, are encouraging higher tipping rates: Is 20 percent the new 15 percent? The confusion is spawning Web sites such as tipping.org, where people share advice. Emilypost.com among other things now offers advice on dealing with the proliferation of tip jars. (Search for “tipping.”)

First, it’s good to know what other people are doing: According to Zagat Survey, the average U.S. restaurant diner now leaves an 18.8 percent after-tax gratuity, up from 16.5 percent five years ago. Generally, when dining out, exceptional service should get 20 percent or more. If other staff, say the sommelier, is helpful, consider a separate tip of 10 percent of the bottle’s value.

For bad service, feel free to give, say, only 10 percent — but only if you’re sure it was the waiter’s fault, as opposed to something out of his or her control (like a blunder in the kitchen). Even if you feel justified, take a deep breath and rein in your anger. Often, waiters divvy up tips with busboys and hosts, who don’t deserve the punishment.

With the exception of restaurants, where staffers can depend heavily on tips because they’re paid below minimum wage, most other tipping is optional. That’s not to say that being miserly is an appropriate default setting for your internal gratuity-dispensing mechanism. “Do it out of a sense of self-confidence and feeling good,” says Tim Zagat, founder of Zagat Survey.

We sought out people with informed opinions to walk us through a few potentially awkward but common scenarios. One recurring theme: A buck is often a good answer.

For bartenders, a dollar a drink is good when you ask them to whip up a cocktail. Think 20 percent on bigger tabs, says David Craver of the National Bartenders Association. Unlike waiters, barkeepers often earn the minimum wage, but still “rely on tips to make a decent living,” he says.

In hotels, make it a buck a bag for bellhops, more if your luggage is out of the ordinary. For room service, restaurant guidelines apply.

Taxi drivers? Make it an even dollar on short trips, and 10 percent to 20 percent on longer trips. Unless, of course, you’re taken for a ride.

Of course, not all advice is made to be blindly followed. One guide aimed at tourists in Las Vegas ( www.lvchamber.com/visit/tipping.htm) has lots of solid guidance. But it also suggests tipping ushers $2 to $5 “… even if you have preassigned seating.” C’mon.