Istanbul has two airports. The major Ataturk International Airport is in the European side of the city, 23km (14 miles) west of the city center and Sabiha Gokcen Airport on the east side of the city, Asian side. Taxis and public transports serve both airports. You can also book a private transfer to reach your desired location.
There are a lot of taxis in Istanbul. Locals use it a lot and you can catch one very easily. Taxis are yellow and you can see the word "Taksi" written on it, which means “taxi” in Turkish. Use always your hotel service to call for a taxi. Taxis in Turkey are much cheaper than in Europe, and it is a common way of transportation in Istanbul.
In Istanbul, city buses are usually slow and crowded, especially during rush hours. You should buy Istanbulkart transit pass to use these buses. However, it is very cheap and you can go anywhere in Istanbul with city buses.
There are a few ferryboats that connect the Anatolian and the European side. During rush hours, bridges are extremely crowded so using a ferry is a better alternative for travel. Ferryboats are also most enjoyable way to travel in Istanbul.
There are two main lines of Metro system and one main line of tram in the European side of Istanbul. The most useful for foreign visitors is the light-rail line connecting Atatürk Airport and Aksaray Square via Istanbul's intercity bus station, at which you can take a bus to any part of Turkey. You should switch to the tram from the Metro at Zeytinburnu to reach Old Istanbul and Sultanahmet Square. Also, a standard-gauge Metro line goes north from Şişhane (Tünel Square) and Taksim Square to the northern commercial and financial districts.