Download Grab before you arrive. It locks in the price, shows the driver, and avoids the meter-tampering scam common in some street taxis.
Mai Linh (green) and Vinasun (white) are the two reputable metered taxi brands if you must hail one. Avoid lookalikes with similar logos.
Grab also offers GrabBike — a motorbike ride for short hops. The driver brings a helmet. It's cheaper and faster than a car in traffic.