1

Welcome to Thorntree. Don't book a tour, independent travel is twice the fun and about half the cost. However, check with your local travel agent or online and get brochures of tours of Vietnam, this will give you the known highlights, itineraries, things to check and known routes. Book your first night or two accommodation of the place you are flying into. Also I found most hotels are helpful in booking bus/train tickets and at very little or no extra cost. Also if you want, get your present hotel to phone through and book your next destination Hotel and also to find out how much for taxi from the train/bus station to the hotel etc. it helps when negotiating with taxi. Also, if you want, the hotel can help organise a small local tour of the area once you're there. So there are levels of independent backpacking but Vietnam is definitely a go it alone place.

2

I found Vietnam to be a friendly place, you'll be fine alone, just be aware of all the scams that you will encounter so you don't fall for them (e.g. if someone compliments on how they like your shirt it's most likely a filipino card scam, read up on that one, because most likely you will encounter it). No matter how smart you are you will get overcharged, you will make bad decisions, you will pay more than you should for some things. That's just SEA, and not knowing a new place, so just factor that in, and don't ever worry about it. Things don't always work as planned, that's just life here, so if you understand that and don't expect everything to go as planned, you'll have a great time. Do not do any drugs or anything else stupid and you'll be fine. The only danger is the traffic, you have to get used to looking both ways constantly. As for taxis just stick to the reliable companies like Vinasun and Mai Linh and you won't be ripped off there either. So don't be scared just read up on it, and go for it.

3

First, make sure that you have visa to enter Vietnam. It is more popular to get visa on arrival (VOA, check the previous posts. Book hotel rooms with online websites like agoda, booking.com etc. Also, book internal flights and train tickets in advance. The day trips and excursions can be arranged by your current hotels. Otherwise, book a group tours with Vietnam Budget Tour.

4

The nerves will go almost as soon as you get there. In 200 days in SE Asia as a visitor I have never had more than the mildest of setbacks.
As mentioned above use reputable companies.

Good luck