By Air: The closest international airport is the Na Boi International Airport which is at a distance of 35 km from Hanoi. There are a number of flights to Hanoi, Vietnam from a number of destinations. The Hanoi airport is small but well equipped and passenger friendly too.
By Taxi: There are fixed price taxi stands right outside the exit, offering fares ranging from US$15-$25 into the city. These are provided by various taxi companies and are slightly more expensive than the tout taxis, but fixed price, so no hassles about the fare. Later into the night, there don't seem to be any physical taxi stand, however you can still negotiate directly with taxi drivers for fixed prices all the same.
By Bus: Public buses to the city centre from Noi Bai airport take about 1.5 hours. There are shuttle buses too that drop you near your hotel at an affordable price.
By Train: Hanoi is well connected to the rest of Vietnam by trains that depart from the Hanoi Train Station. One can also board a train to China from Gia Lam station.
HOW TO GET AROUND HANOI
By Cab: In Hanoi, a taxi driver is quite a colourful character. He will play you, fool you and show you around the entire tourist places in Hanoi a little more than you asked for. Beware of drivers that will try their best to take you on the most expensive ride of your life. Also, be very careful with meter taxis in Hanoi. Meters have been known to operate "normally" initially, but after you've let your guard down, it jumps to astronomical amounts just before the destination. Ask around for reliable taxi operators and stick to those.
By Xe Om: Motorbike drivers ("Xe Om" in Vietnamese) can be found on virtually every corner, especially in the Old Quarter. Expect to be offered a ride every half-block (or more). You should absolutely negotiate a fare in advance. Having said that, travelling by Xe Om is an excellent way to experience Hanoi sightseeing.
By Cyclo: Cyclos are cycle-taxis that are quite common in South East Asia. Negotiate prices in advance and be quite firm about them. If you chose to travel by Cyclo, be clear on your destination, negotiate your fee first, be willing to get out and walk away, also be willing to walk away at the end of the journey if the driver won't stand by your original agreed price.
By Bus: Buses in Hanoi are well connected albeit a bit difficult to comprehend at first. Take your time and get to know the routes before you actually board one.