At Restaurants: Scan the bill first: The gratuity usually isn't included, in which case you should leave about 10 percent, preferably in cash, and a bit more if you tip on a credit card. If the gratuity is included, throw a few more bills in on top.

At Hotels: Give the concierge about $20 if he does you a favor (like securing special reservations outside the hotel). Cleaning staff get about $2 a day, left at the end of your stay on the nightstand, where it's easily visible. You don't need to tip doormen.

Guides and Drivers: Guides get $15 per person per day and drivers half that, given at your last encounter if you venture out more than one day. You don't need to tip taxi drivers, but you can round up the fare (so if the fare is 45,000 dong, leave a 50,000-dong bill). Work out the fare in advance with drivers of cyclos, or bicycle carriages, which are common and usually charge about $10 per hour. It's okay to add on a few dollars' tip.

Dollars Accepted? Yes.

P.S. Tip a massage therapist in a fancy spa $5 to $10. If you go to a days-long spa—the kind "where they make you drink green tea till it's coming out your ears," says Ferguson—they'll tell you the tipping policy in advance. "Bring all the $2 bills you can," advises Ferguson, "and use them to tip porters. The $2 bill is rare in Vietnam and is considered lucky."

Source : CNTraveler.com