All flights arrive and depart from Delhi's Indira Gandhi International Airport, along the southwestern edge of the city. It has separate domestic and international terminals that are quite a few miles apart, though connected by a free hourly shuttle bus.
The airport is about a 45-minute drive from Delhi's center in light to moderate traffic (i.e., before 9 am or after 8 pm).
Major hotels provide airport transfers, otherwise taking a cab is your best bet. To avoid being overcharged, use the prepaid taxi service from a counter near the exit. Unfortunately, hucksters have set up similar services; ignore them. Your destination determines the fare, to which a small fee for each piece of luggage is added. Pay in advance at the counter, then take the receipt and exit. When you get outside, people might try to help you with your luggage; ignore them also, and make sure they do not touch your things. Wheel your luggage down the ramp toward the black taxis with yellow tops, at which point the drivers will appear. If your receipt contains a taxi number, use that cab; if not, the drivers will decide among themselves who should take you. Tell the driver where you're going, and hold on to the receipt until you arrive. Tips are not expected unless they help with your luggage.