Hot. And wet. These were the first impressions of Hanoi. But then, the beauty of this city comes into foreground. In the shades of many trees growing along the streets, you look up to the fronts of the old buildings, see the friendly people doing their daily task and breath the air leavened with nameless smells. Millions of scooters on the streets, carrying sometimes a whole five headed family or seven crates of beere.
A lot of the interesting signs are reachable by feet, but sometimes it is just to good to jump into an air-conditioned taxi. One thing we learnd very fast: do not choose a taxi waiting for passengers! They will rip you off, e.g. they will try to bargain a price to the destination, or the have a manipulated taximeter (so you pay triple the normal price). We always tried to catch on of the MaiLinh company since we always had good experiences with them (there are also fake taxis with nearly the same name on the roads - take care ;), but there are different companies that are also reliable.
The hotel we stayed in Hanoi was the Indochina 1. Clean, friendly, well priced and very well located in the old quater. It was a great help that they offer a pick up service at the airport - after so many hours in the aircraft it is so good to find a nice person waiting for you with a sign in his hands with your name on it.
Food is no problem, there are plenty of nice and unexpensive restaurants around in Hanoi.
Last tip: if you would like to visit the Water Puppet Theatre, by your tickets as early as possible, at least one day before you plan to go there.