Singapore's Changi Airport, like the city, is a modern and efficient international airport. The international airport code for Changi is 'SIN'. Like most airports, the departure hall is above the arrivals hall. There are currently four terminal buildings. Terminal One is used by most international airlines, while Terminal Two is used almost exclusively by Singapore Airlines. A special terminal for budget airlines opened in March of 2006. A fourth terminal building, perversely called Terminal Three, opened in 2008.
The three main terminal buildings are linked by an automated train, both on the 'land side' and on the 'air side' secure area. It is also possible to walk between the three terminals within the departure area. Note that, since Changi is (more or less) the only scheduled airline airport in Singapore, there are no 'domestic' departures.
For more information about Changi Airport, see my own Singapore airport guide, or www.changi.airport.com.sg.
Singapore Arrivals
Arriving passengers exit from the plane into the departure area. There is no separation between arriving and departing passengers. Follow the signs to immigration and baggage claim, which are downstairs. You pass through immigration first, then on to baggage claim. After getting your bags, you exit through customs into the arrival hall.
Singapore Airport Transfer
There are several options for getting from the airport into the city center, or elsewhere in Singapore. If you're traveling light, with just a small carry-on bag, then the cheapest and fastest option is the subway system, the SMRT. The fare to just about any part of Singapore is less than S$ 2 (1.27 USD). Note that trains from the airport go only as far as Tanah Merah station. From there you must change to a west-bound train. On that note, you should check into how many train changes you may need to make. While transfers between the east-west ("green") line and the north-south ("red") line are rather easy, transfers to the north-west ("purple") line generally involve a rather long walk and one or two escallators. It's not a trip you'd like to make if you've got a lot of luggage.
In addition to the train, there are two other options: the airport bus and taxi. The airport 'bus' service actually utilizes van taxis, which are shared among several passengers heading to hotels in the same area. A taxi will cost you around S$ 15 (9.49 USD) to S$ 20 (12.65 USD), while the bus is only S$ 7 (4.43 USD).
Although transfers are quick and easy at the airport, if you're arriving at an odd hour or in a small group, you may wish to book a transfer in advance:
Singapore Departures
Leaving Singapore through Changi is quite easy. The hardest part may be showing up at the right terminal, although most taxi drivers know which airlines fly from which terminals. After check-in, you can proceed through immigration and into the lifestyle shopping palace that is Changi airport. There is no departure tax.
Singapore Airport Duty Free
The shopping at Changi Airport is among the best in the world, and significantly outclasses just about every other airport in Southeast Asia. There is not only an ample selection of the standard duty free items of booze, cigarettes and perfume, but also a wide variety of other items. There are many small designer boutiques, electronics shops and even some traditional medicine stores. See my duty free guide for benchmark prices.
You won't go hungry at Changi either, since the airport has several food outlets selling a wide selection of foods, from sandwiches to sushi. There is also a movie theater in Terminal Two, as well as several airport lounges.