They say there are four to five million motorbikes in Saigon. Here is a video I found on Youtube that shows what traffic looks like.
So you may wonder what prepared me to drive in such traffic. After the basics of learning to ride a bicycle (thanks Dad) and a car (thanks Mom and Dad) I think playing (American) football with my brothers was the most helpful. Specifically practicing punt returns.
In a put return you have people coming at you from all different directions and your goal is to get to your destination without getting touched. To do this you try and determine on the fly which direction the opponent is coming from and use your blockers to help you get to the goal.
The same is true with driving in Saigon. You are heading toward you destination and you have to avoid all the other motorist who are coming at you from many different directions (driving on the wrong side of the street, doing a U turn, or trying to cut across all the traffic lanes to get to a street on the other side). Generally they too are trying to avoid you. If you need to cross into on coming traffic then it's best to look for you blockers (in this case Buses work best, then cars, and finally other motor bikes). The first person who is looking to make a turn into traffic will start off and create a wedge and then you and likely others will follow that wedge until you succesfully make the turn (look for it in the video.
While it seems very chaotic it seems to work pretty well. I've seen very few accidents.