When you are arriving, you won't have a sim yet. So forget Uber type options. Besides taxis are easy and cheap. I never heard about taxi booking in the terminal (because I don't speak Viet like Yoda?) Anyway it is easy to avoid the taxi scam, and don't worry about getting robbed.
Steps:
1. Come with a piece of paper that has the name and address of your hotel and "District 1", in big easy-to-read-at-night letters, because you can't speak Vietnamese.
2. After immigration, you go downstairs, find your bags on the carousel, then if you are not declaring anything (right?) look for the sign to exit customs.
3. You are now in the lobby. Welcome to Vietnam. There will be ATMs and some people selling SIMs and currency exchange. I always use the ATMs because I like to save my US dollars for emergency. (Note: your dollars/euros must be in like-new condition and they like $100s best. Suggest you bring 10 or 20 of those Benjamins as backup in case your ATM card fails like mine did last week). Get at least $50 worth of Vietnamese dong, you are now a million-dong-aire.
4. Go outside and the hot air will hit you in the face. There will probably be hundreds of Vietnamese greeting you. No, not you, kidding. Head straight through the crowd and ignore everyone who talks to you. There is now a "good taxi" island, you have to cross one or two traffic lanes, can't remember.
5. The taxi queue is a long aisle and you drag your bags to the head of it. There will be a woman who will ask "Where are you going". Show her the paper. Say one word: Vinasun. That is pronounced "vee-nuh-soon". They will understand why you request that company. Probably all the taxis in the queue are legit though, but I always insist on veenuhsoon even when I am with my Vietnamese wife.
6. The lady will give you a slip of paper with the taxi name and some official statements because this is how they keep the taxis honest.
7. Show the taxi driver your hotel address. Doesn't hurt to make sure the meter is running, starts at 15 or 20? I can't remember, short for 15,000 etc. If you are worried, you can sneak a photo of the driver's badge with your smartphone.
8. While driving, watch your google map on your smartphone (should work without a local sim *) and start to get an idea of the city layout. You can also monitor that the taxi is taking a fairly straight route southeast.
9. My last trip to the airport was 4 weeks ago but from D7, it was 186,000d in traffic so you will pay less to D1, maybe 120.000d at that time. You never need to tip.
10. Next day you can get a sim from your hotel or the hotel will tell you a store to go to. Costs something like 100,000 for the sim, 100,000 for voice and data per month. The shop will install it. Put the XE app on your smartphone for conversions.
ok that's it!
* correction: Go ahead and download the Saigon map and save it locally on your smartphone before you come. Google for instructions.