Istanbul Transportation, Getting Around the City
In Istanbul there is a hierarchy for mode of transportation that you should follow for ease and enjoyment of your trip in the following order from most desirable to least: your own two feet, ferries and sea buses, tram, metro, metrobus, bus and if necessary taxi. Dolmush and minibuses are difficult even for Turkish people but sometimes they maybe necessary.
If you plan on using public transportation, you should buy an Istanbul Card as soon as you arrive. This will save you the time and the trouble of buying token everytime you use public transportation. It is a card you touch at turnstiles to pass. You can load credits (starting around 4 euros/6 dollars) for travel on the bus, tram, seabus, ferry, tunel, metro basically all public transportation. You do not need to buy multiple cards if you are two or more people traveling together, you can use one card, pass and give the card to your companion.
If you must get a cab have the taxi called from your hotel front desk or if you are out in the city look for a company name on the side door so you'll know the cab is not independant but working in association with a company.
Ferries and Fast Ferries
Use classic Istanbul ferries (photo above) to cross the Bosphorus from Karakoy, Eminonu, Besiktas to Kadikoy or to go on a Bosphorus cruise or to Prince's Islands. The classic big ferries are ideal for sightseeing. Fast ferries also known as sea buses (Denizotobusu in Turkish) are of great use if you want to reach your destination faster.
You may also use Seabuses to go out of Istanbul to southern Turkish destinations via Bandirma. Please note these ferries need early reservations for most of the summer months. There are also ferries that go to location in Marmara Sea such as Marmara and Avsa islands and Yalova and Cinarcik.
For travelers the most important rail network is the tram that goes from Kabatas (down from Taksim via a connecting one stop metro) passes through Eminonu, Karakoy and Sultanahmet and goes in the direction of Bagcilar, Zeytinburnu or Cevizlibag. These three stations are in the same direction but some trams do not go until the end of the line which is Bagcilar but stop short at Cevizlibag or Zeytinburnu. The last stop is marked so on the electronic sign of the tram. For most travelers this does not make any diffence because allof them cross the major tourist stops of Beyazit, Aksaray and Topkapi districts. Note: the tram maybe crowded.
You could certainly use Tunel, one stop metro from Karakoy to Tunel or the funiculaire from Taksim to Kabatas.
And there is one metro line of potential interest is the metro that goes from Taksim to Haciosman.
Please note this Map of Istanbul Rail Network is useful only for people who will stay in Istanbul for a long period of time or who stay in remote corners of Istanbul as most lines are outside Istanbul's main sights. Also suburban trains are not of use for most travelers.
Buses reach everywhere but they are most of the time too crowded. Metrobuses are quick and cover big distances in Istanbul but they are also packed.
Green colored municipality buses and an airport bus transfer company has shuttles to some destinations in the city. You can also get Istanbul Airport Transfers to any destination in the city or nearby towns at reasonable rates, instead of a taxi.
Cruisehips arrive right in the center of Istanbul, Karakoy. You can easily go anywhere with a short ride to Taksim, Sultanahmet, or the Bosphorus area Besiktas and beyond.