By plane

Tan Son Nhat (Tân Sơn Nhất) is Vietnam's largest international airport. You can fly direct to SGN from Siem Reap, Phnom Penh, Bangkok, Phuket, Kuala Lumpur, Singapore, Bandar Seri Begawan, Manila, Macau, Hong Kong, Taipei, Kaohsiung, Taichung, Nanning, Shenzhen, Guangzhou, Beijing, Shanghai, Kunming, Seoul, Busan, Tokyo, Osaka, Fukuoka, Nagoya, Doha, Frankfurt, Paris, Moscow, Perth, Darwin, Sydney and Melbourne. There are two terminals: the new international terminal, which took over all international flights in 2007, and the old terminal, which is reserved for domestic traffic.
By bus from the airport
The recently introduced No. 152 air-conditioned airport bus is the cheapest way to the city from the airport. For about 3,000 dong, it will drop you off on the west side of the Pham Ngu Lao area, or at the bus terminal on the south side of the Ben Thanh Market roundabout. Upon exiting the airport, turn right and walk towards the domestic terminal - about a 5 minute walk. In front of the airport across a small road, you will see the bus waiting there. Note: Ignore taxi drivers that may tell you there are no more airport buses. However, the bus is only available until 7 pm.

By taxi from the airport

In lighter traffic periods (which usually only happens between 12 midnight and 6am), taxis from the airport to the city center will usually take as little as 15 minutes. During these lighter traffic periods, this should cost no more than 90,000 dong. More typically, taxis can creep along in near-standstill traffic for an hour or more. During these heavier traffic periods, taxis will cost about 120,000 dong to 150,000 dong from district 1 (inclusive of airport tax). .
Car Rental Service Drivers Recently, Budget Car Rental became the first international car rental company in Vietnam. They offer English speaking drivers and new model vehicles, one trip to the city costs fixed price of 140,000 dong.
Departure / Leaving HCMC When you going to the airport, be specific which terminal you want to go to. International flights go from the newer international terminal (go straight); Domestic flights (to Hanoi, Danang, Nha Trang, etc) are from domestic terminal (turn left).
If you get dropped off at the wrong terminal, you'll have to dash your way to the right terminal via pedestrian walkway link 600m away. This is not recommended, especially if you're already late for boarding.
When entering the airport, taxi drivers will add an entry fee to your total meter. This is for the airport entry fee (5000 dong). Don't confuse this entry fee with the "Airport Departure Tax" as International Departure Taxes should have been included in the price of your flight ticket. As of November 2009, going from Ben Thanh Market to the airport at noon, the total fare is 80,000VND using the green and white metered taxis (VinaSun and Mai Linh).

By bus

If you take a bus, you will end up at one of the following bus stations:
•    Cho Ben Thanh Bus Station - This is right in the centre of HCMC, in walking distance of the tourist sites and accomadation
•    Mien Dong Bus Station - Buses heading north leave and arrive here.
•    Mien Tay Bus Station - Take bus 139 from Tran Hung Dao Street to get here.
•    Cho Lon Bus Station
From these stations, public buses in around the city will cost you about 3,000VND.

By train

The train station GA Sai Gon is on Cach Mang Thang Tam (CMT8) North-west of the city center, and is a short taxi or public bus ride away from the main hotel districts.
There is an official train ticket office located at 275C Pham Ngu Lao.

Travel Tips: http://www.vietnamwiki.net/Ho_Chi_Minh-Tips-Tips_when_traveling_to_Ho_Chi_Minh_city-P188