How do I choose a travel agency to book tours from in Hanoi, Vietnam?

I agree with Jozzas. It doesn't really matter.

I recently returned from Vietnam. Most hotels that you stay in at Hanoi have tie-ups with some tour operators, especially for tours to Sapa and Ha Long Bay. I did not travel to Sapa, but we had our hotel book us a 1 night-2 day Ha Long Bay tour. We travelled with Cristina Cruises on their Vietnamese junk boats. It was a wonderful experience, and we had a good time. We did not go to Cat Ba Island but were taken to one of the biggest Cave islands in the Bay. But most cruises offer a variety of options that you can pick from.

My recommendation: check with the hotel you are staying with if they have any tie-ups with tour operators, and go with their suggestion. There are many tour operators in Hanoi (if you walk through old market streets you are likely to be confused with all the tour offers). I would not recommend more than a 1 night - 2 day cruise on Ha Long bay, though.

For Ha Long bay from Hanoi you can just get yourself a bus ticket from the bus station. If you are considering Ha Long Bay also consider Cat Ba Island. I have heard mixed reports of Ha Long Bay tours. I was warned a really cheap tour is generally a really bad tour but I rock climbed with a guy on Cat Ba Island who took a cheap tour and said it was great. I think the quality of the sleeping on the boat was generaly the issue. I travelled by bus to Cat Ba with Hoang Long Bus Company. I think they go to Ha Long city as well. If you buy a Ha Long Bay tour though, it may include transport from Hanoi.

If you don't have a lot of time - like one week or so - you should book a tour online. But if you have around one month come to VN and take the tour from hotel or local agency!

Halong Bay - (should take packet tour)- check weather forecast before booking the tour

Sapa - if you want freedom time just book transfer to there and take tour or do it yourself hen you be there that is easy way!

How to get south:

Hue - one day (from Hue to Hoi An). If you are not scared of heights I recommend motorbike way. That is imagine way!

Danang - Hoi An two days - three days! Visit my sons temple - Cu Lao Cham Island - Hoi An (the best place to make tailor like suite, dress, shoes, etc).

Nha Trang - or Mui Ne for relaxing beach

Ho Chi Minh - one or two days - Mekong Detail - Cu Chi Tunnel

Phu Quoc Island is a beautiful beach.

You can get more detail when you arrive.

Have a good trip!