For the tour guides and the drivers
For an excursion with a tour guide and private driver, it is advisable to tip the guide and the driver at the end of the service, depending on the relationship they have created with you during this day and the quality of the services provided such as language or small touches.
For example, give 250,000 VND per day for the guide, and half for the driver.
For your cruise on Halong Bay think about the crew and the tour guide.
It is customary to tip separate for guides and drivers.
In hotels
As a rule, 40,000 VND tip for the hotel staff as the person who helps you with your luggage or the maid.
In cafes or restaurants, tip is not essential, you leave the difference of some Dong.