Istanbul is a large, bustling city and its crammed with people. You will enjoy your visit much more if you know how to get around before your arrival.
AIRPORTS
Istanbul has two airports, the major one Atatürk International Airport (IST) is on the European side and is reachable by Metro; and Sabiha Gökçen Airport (SAW) is on the Asian side of the Bosphorus. Atatürk International Airport is located in Yesilkoy, 25 km outside the city center (Taksim). Sabiha Gokcen Airport is located in Kurtkoy/Pendik. Taxis and public transportation (IETT) serve both airports, but a private transfer maybe a better choice for some travelers. If you can not afford a taxi, you can use the Havas Bus service that will take you to Taksim, the city center. After arriving in Taksim, you can take a taxi to your hotel.
HAVAS BUS
The Havas bus service can used to and from both of the airports. It is considerably more comfortable and runs directly to and from Taksim Square. It is the most convenient choice for travelers staying in Beyoglu. For up-to-date information on schedules and fees for airport transportation, you can check the website here.