On foot is how you see the Old Quarter and the French Quarter. Everything of interest downtown is within a 20-minute walk.
Grab (the local Uber equivalent) is the easiest way to get further. The app handles cars and motorbike-taxis, and prices are transparent.
Taxis are plentiful but notorious for meter shenanigans; stick to the Mai Linh (green) and Taxi Group (white) brands, or use Grab.
Motorbike taxis (xe om) are the fastest way through traffic — flag one down or book via Grab Bike. Always insist on a helmet.
Cyclos (bicycle rickshaws) still exist, mostly for tourist loops of the Old Quarter. Agree the fare before you get in.
Metro. Line 2A opened in 2021 and Line 3 is partially open; both are limited but cheap. They are useful for a few specific journeys but not for most tourist itineraries.