By Air - There are airports in Hanoi, Ho Chi Minh City, Nha Trang, Da Nang, Hue, Da Lat

By Train - There are trains from Nanning and Beijing  (China) both bound for Hanoi

By Bus - Yunnan and Nanning (China), Phnom Penh and Siem Reap (Cambodia), and Vientiane (Laos)

November to February - cool weather in the dry season, best to travel around

March to April - hot weather in the dry season, easy to get sunburnt

May to October - Rain season, always rain and highly humid, chance to encounter typhoon along beach cities.

Vietnamese Dong is the currency used in Vietnam. 1 USD is about 23k Dong. Be prepared to be a millionaire in Vietnam. You will realise locals tend to skip three 0 when they are telling you an amount. If you need to exchange more cash, most of the travel agencies or jewellery shops normally provide this service. Alternatively, you can just withdraw from ATM but on a lower rate.

You can get a SIM card after you come out from the immigration and there are plenty of brands with similar packages. There is no much difference so just choose the package that suits your days of trip the best. Some very useful apps will be Grab, Booking.com, Agoda, Hostelworld, Skyscanner, World Nomads, 12go, Rentalcars.com.

From city to city, flight is always the faster choice. But if you want to be more cost-friendly, sleeper bus is the thing that you should not miss. Journey between cities with shorter distance, limousine van is slightly and acceptably higher in price but much more comfortable than a coach. Within a city, you can always walk or if not you can just use Grab app to get a motorbike or car ride. Motorbikes and bicycle rentals are also available in most of the cities. Bus is very cheap but mostly are for locals and it is not perfectly convenient unless you do not mind to spend some time using body language to get to a destination.