With only a month's head start on knowing when my vacation would be, I took the fast mail route on a $65 visa for Vietnam through their embassy in Washington DC. I sent it in 2 weeks beforehand and got it back just days before I flew to Southeast Asia on my trip. There are now a lot of direct international links into HCMC, and gateway flights are from Singapore, KL, Taipei, and Tokyo, and Korea now, as well as Bangkok. Unfortunately, the flood of new tourists has not changed up the rate or number of immigration control officers at Tan Son Nhat. Here is an airport that you do want to be first off the plane at! This is also a place where its better to hit the restroom before you land, because the wait in line may be well over an hour, and you are not going to want to get out of it and join another line. People waiting on you outside know that it will take you an hour to get through customs and get your bag. The rule of the road is if you get through immigration fast, you will have the last bags coming out.
My first time into Vietnam, I was unsure how the immigration officers would act and was a bit intimidated, but I have not had a problem in three trips there. After you go through immigration, you will pass by some duty free shops. If you are meeting Vietnamese friends and want to pick up a bottle of something or chocolates, you can do it as you are going to pick up your bags. It's sometimes a surprise how long it takes your bags to get through, but collecting them and showing the ticket is all pretty easy. There is an exchange before you go out the door; fork over about $20 there and you are set. The culture shock for Vietnam begins as you pass through the doors and you see hundreds of people waiting.
Unfortunately, the first people you tend to meet are folks I call "snakes". A "snake" is a cab driver who moves in and preys on tourists arriving in country and harangues and harasses them into riding with him – usually at a rate that is up to 50% above what the guys waiting in the crowd will charge. In Saigon, a couple of them will immediately move forward to you as soon as you clear through the doors. I usually push past them, saying I already have a ride and go on to the taxi stand and negotiate for the ride with them. I had a snake charge me $20 for a ride to a downtown hotel – after a breakneck ride that rivaled anything out of the Dukes of Hazzard. You should be able to get a cab for less than $15 (counting tip).
Returning to the airport, you find a crowd outside again – but not one after you go through security. There is a $12 exit fee from Vietnam that you will need to pay and later present this when going through immigration. There are few stores or shops in the airport, but you can purchase some last-minute Ben Tre coconut candies at the bigger duty-free Store. Food items in there are priced only a bit higher than outside – the rest of the items I hope you already got in the many markets of Saigon!
If you are flying to another city in Vietnam, you do not have to pay the fee. One item of interest was that the weights of bags on Inter-Vietnam flights was different than International flights, so you may have to pay $1 or $2 for overweight bags. The airlines will point you to counter 22 or 23 and have you go there to pay the money and then return to collect your boarding pass.