Here’s my personal itinerary. I decided to skip the beaches, which are supposed to be gorgeous, because I had already spent enough time on Thailand’s beaches.
Well, this is quite a broad subject… Are you asking for places to see, things to do, or general tips?
First tip is to do your research. Vietnam is a long stretch of land and there’s a lot to see. If you have limited time, you probably have to pick a few cities you really like. You can ask for recommendations on Quora but everyone has different preferences, so I would start with Wikitravel for a simple overview and go from there.
Here’s my personal itinerary. I decided to skip the beaches, which are supposed to be gorgeous, because I had already spent enough time on Thailand’s beaches. Instead, I (or my group) chose the following:
Hanoi Vietnam – For its history and museums, and access to Halong Bay/Sapa
Halong Bay – UNESCO site and natural beauty
Sapa – Hidden in the mountain with traditional villages and rice terraces
Ho Chi Minh City/Saigon – I would say this is what I imagined modern Vietnam travel to look like. Also if you want to experience good night life and visit the Cu Chi Tunnels. Can add a side trip to the river deltas as well.
Other places I would have liked to visit are Hoi An, Hue, Da Nang, that are more in the central part of Vietnam.
Other random tips:
– Vietnamese food is amazing. I did a foodie tour in Saigon (on the back of motorcycles driven by cute Vietnamese girls in traditional dresses!) and it was wonderful.
– You can’t get into nice clubs with flip flops :/
– Egg + coffee. Why don’t they make those here?
– Rent a scooter and ride around the country if you are the adventurous type.
– When crossing the street, just walk and don’t stop. The motorcycles look like they are running you over but they all know how to avoid tourists.
– When in Halong Bay, there are the party boats, and there are the slightly-more-luxurious-boats-where-people-go-to-bed-at-10.
– Cipro works wonders.