Don't be surprised when you are flying out of Hanoi and you have to pay US$14 departure fee! We had no clue and no one bothered to mention to us until we were through security and going through customs... We almost missed our flight, backtracking to pay this tax. Not to mention they wouldn't let us carry our bags back out through security, so we let them sit in the middle of the airport with thousands of people milling about. Not a pleasant experience.
Hanoi Airport is new and modern, quite a contrast from HCMC's Vietnam War-era airport. The only problem is its location, quite a long drive from the city. Not as many airlines fly into Hanoi as into HCMC, so you may have more trouble getting here. We flew Vietnam airlines from HCMC to Hanoi, then again from Hanoi to Seoul. The hour-long flight sure beats the day-long train trip.
Be aware of the exit tax when you depart the country!
The airport tax over here in Hanoi is more expensive compared to the one down south. Remember to reserve $14USD when you're exiting out of Hanoi. Yes, these folks accept dong too. So that's roughly...224 000D.
After two transfers in Los Angeles and Seoul, we arrived in Hanoi 20 hours later (a day and a half with the time difference.) We used our United miles and flew on the Korean airlines, Asiana.
Fortunately for us, we arrived in the evening, and after so many hours in the air, we were ready for some sleep! This allowed us to get up early the next morning with minimal jetlag.
Travel by air can be considered the fastest and of course costing the most as compared to train & buses.
If you can't stand the numb butt for travel by bus for 12 hours or more, travel by air is the best option.
I fly Malaysia Air Line (MAS) to Saigon & the moving up north by busses (Saigon-Hue) & train (Hue-Hanoi).
Hanoi airport is 35 kms away from the center, it will take you 45-60 minutes to get there. There is a minibus of Vietnam Airlines that costs 2 USD.
It leaves from the airport's main exit, just look for the yellow minibuses. U pay once there.
From the city, go to the corner in front of the Vietnam Airlines office, Quang Trung with Trang Thi streets, near the south west corner of the Lake.
Hanoi has a modern medium size international airport. Coming from Europe, the best deals are from the old metropolis, Paris. Air France has manyplanes to Hanoi and HCMC.
There are few Duty Free shops here, so make your shopping in the city before leaving...
If you're not already in Vietnam, by air is the best bet.
I like cyclos, and they are environmentally friendly, but motorbike taxis will get you there quickly, and the drivers are surprisingly honest on prices.