Hanoi is referred to as the "Paris of the East" due to all of its French influences. It was under French rule until 1945, and was an administrative center for the French colony of Indochina. The French colonial architecture is dominant around the city with beautiful tree-lined boulevards (e.g. Phan Dinh Phung street), several lakes, villas, and historical monuments like the Grand Opera House, St. Joseph's Cathedral, and the historic Hotel Metropole. The center of Hanoi is Hoàn Kiếm Lake and all the areas are wrapped around the lake with The French Quarter to the south and east, The Old Quarter to the north, and Tây Hồ to the west. Like anything in Vietnam, hours of restaurants and flight schedules can change at a moments notice, so be prepared to be flexible.
Hanoi is a city that has built a reputation for their French Colonial Architecture, Coffee House Culture, Socialist Art, Confucian Values, and Buddhist Temples. While Hanoi has some really beautiful antiques, exporting them back home is rather difficult, so my advice is to stick with the small objects that you can easily store in your luggage. Hanoi specializes in horn, and you can get just about anything in horn at a fraction of the price that you would find it for anywhere else. The quickest way to get around town is by motorbike. If you don't have access to one, you can hire someone for VND 20,000 (less than $1 USD). Uber is super efficient and very inexpensive; a ride for about 30-minutes will cost you less than $2 USD. Be prepared to encounter some of the friendliest Uber drivers, as they will literally get out of their cars, park, and search the streets to try and find you if you are lost. However, you must prepare yourself for traffic and crossing the streets in Vietnam. They have continuous movement, so there aren't any stop signs, street lights, etc. The key is to always remember that motorbikes can dodge you, cars cannot.
When traveling to Hanoi, make sure to have a lot of cash on you for motorbikes, taxis, street food, etc. Most shops will take USD, so you're fine bringing cash (they actually love the American money!). Tết (Lunar New Year) is celebrated from Mid-January through Mid-February. During this time, most shops close, but if you are there during the holidays, you will see many of the vendors vibrant decorations around their shops and on the streets. The best time to visit is between October- December, as January- February can be a bit chilly or rainy, and May- September is hot, hot, hot! If you are looking to get outside of the city for a few days, try a Hạ Long Bay cruise on a junk boat or one of the luxury ships and have the most out-of-body experience seeing the gorgeous natural limestone formations, natural grottoes, and floating villages. PS, Hello in Vietnamese is: Chow Chee (to gals), Chow Anh (to guys).