*Eat baguettes for every meal with homemade pate and laughing cow cheese spread.
*Go to Cafe Mocha right next to the Cathedral, next to the lake and sample the Red and Yellow beer at breakfast. Produced by their own micro-brewery. Breakfast, lunch and dinner there is also an excellent choice.
*Emperors restaurant in the old French Consulate. Best restaurant in Hanoi. Have travelled there about 10 times and always book one of the tables on the balcony. Fantastic.
*Eat at least 15 times a day....wonderful
*Chill out at night, slowly walk around the lake and relax. Stop off every 15 minutes to eat, drink beer and relax further.
*Drink Vietnamese 'drip' coffee with thick and sweet condensed milk....try every variety you can find. Small glasses often is the best way.
*Get out of bed before 6, and eat noodles and soup at a street stall with the grannies and taxi drivers.
Food, food, food, food. An incredible city full of incredible people. Try and get there for Tet sometime and watch the fireworks around the lake with a million happy people.
Oh, and all the other stuff people said
. Also the Perfume Pagoda tour is good - worth a 1/2 day excursion. The water puppet theatre was also great - they have daily shows. You've got to go see Uncle Ho's body (tad macabre and totally surreal) but check first to make sure that he hasn't gone to Russia for his annual touch-ups. However my favourite memory of Hanoi is strolling around its lake in the old quarter, watching the city come to life at 5am in the morning, still shrouded in early morning mist - the flower sellers gathering their flowers, the aerobics session involving middle-aged women dancing to Kylie's "I Should be so Lucky" whilst 10 metres on, people practise Tai Chi in fluid graceful moves. 
