I’m very keen on taking cyclo ride when I was in Hanoi last year, and I think it’s worth taking a cyclo for an hour only or at the start time of your visit in Hanoi. Some friend advise me walking will be better, but I think the perspective you get from a cyclo ride is worth seeing — plus it’s far easier to look around and take photos if you’re not watching where you’re walking the whole time. And you just have a relax seat on your cyclo to see all small corner of old Hanoi street, that the big van can not do for you. But poor rider, they have to ride hard to make moving cyclo for 2 big persons on. Of course, if you want to explore and investigate the back alleys and stop off here and there, that’s not possible on a cyclo, but an introductory ride will help you get your bearings.
Hanoi is just big enough that it makes sense to take a cyclo tour through the city to get your bearings. As in Ho Chi Minh City, prices are negotiable, but you should be able to hire a cyclo for $1-$2 (15,000 to 30,000 VND) per hour.
A great way to get around and see all the interesting back streets of the city is to take a cyclo tour. As we were with a tour group, we ended up travelling in convoy which provided us with the opportunity to take photos of each other. (there's only really room for one fat Western bottom in a cyclo!) The drivers worked really hard to speed us through the streets and protected us from the other traffic; mainly mopeds. Take the time to look at all the places you want to get a closer look at later, then I challenge you to try and find them again!!
Our hotel helped us to arrange for 2 cyclo drivers (one for each of us) to give us a tour of Hanoi. Based on their recommendation, we went to the Ho Chi Minh Mausoleum, the One Pillar Pagoda, the Temple of Literature, the Hanoi Hilton and around the Old Town.
We did not have to deal with them trying to take us to any shops where they knew we could get a "deal". They were very helpful and polite. They waited for us patiently as we toured each of the stops. It was an adventure in itself to experience life in the middle of the scooter traffic.
The cost was US$2 per person per hour, and we also gave an additional tip for the good service. It was a great deal and a great way to experience Hanoi.
Our tour was arranged through the Sofitel Metropole Hotel, which has their own group of cyclo drivers waiting outside at all times. However, I am sure you could arrange a similar tour with cyclo drivers on the street - they will offer you a ride wherever you go.