Depending on traffic and how fast your taxi drives, the center of Istanbul is 

about a 30 minute drive from the airport.  The easiest way to get from the airport to the

city centre is by taxi.  The fare will be approximately US $15.  (Note that from 12

midnight to 6 a.m. there is a higher night rate (gece on the meter; the day rate is

indicated as gunduz) in effect and as discussed below, taxi drivers do not expect tips).

Taxis (all of which are painted yellow and have a sign on top of the cart that reads

Taksi, the Turkish word for Taxi) are available as you leave the arrivals hall.  At peak

times, the area outside the baggage claim area is a bit congested and you should

proceed directly to the taxis located outside the building.

Taxis are cheap and reliable in Turkey.  Taxis all have meters and while the

drivers generally don't speak English, they are usually fairly friendly (except to other

drivers).  Make sure that you ask the driver to take the road by the sea, and not the

motorway, to the city (you should say Deniz Caddesi, pronounced De-neez Jah-de-see,

in Turkish)  The motorway is a longer distance and is not as scenic.

Turkish taxi drivers do not expect tips and should not be tipped.  Note that taxi

drivers never have change and you should always carry plenty of small notes.  Note:

While most taxi drivers in Istanbul are very honest, be careful of the taxi drivers that

hang out near the tourist areas, such as the Grand Bazaar and Aya Sophia.  These

drivers will often request a very expensive flat fare for short trips, which often is double

or triple the meter fare.  Also, even if the taxi driver uses the meter, they may take

tourists on a circuitous route.