If you have never visited Ho Chi Minh City before, and particularly if you have never visited Asia, then it is a good idea to understand that the traffic moves in a different way that at home. The roads are filled with dense traffic - predominantly motorbikes and the occasional taxi. 

The first thing to understand that it moves like water in a stream around a stone. The trick is not to do anything erratic - stopping is just as dangerous as moving too quickly. Vietnamese people are used to slowly moving around pedestrians so any unexpected movements may make things difficult for everyone. 

There definitely are rules of the road but they are different - probably because if you have a full road of motorbikes they have a lot more flexibility than a couple of lanes of cars.

The following video gives a good idea of what to expect as regards to traffic in HCMC if you'd like to prepare yourself for your adventure. Don't watch this if you are afraid of driving... 

Time lapse video of traffic in HCMC by Rob Whitworth

Things are a little calmer in Hanoi, and if you get to Hoi An or Hue then there is much less traffic again but the same principles apply.  

Finally if you still aren't feeling confident find a friendly looking older lady and stick close. Follow an expert!