Buses in Istanbul are cheap and frequent. They cover the entire city, and are often the best way to get around in the absence of the trains. Some of the major transfer hubs are at Eminönü, Taksim, and Besiktas. Commuters can purchase tickets at any of the major hubs or at the stations. Istanbul's public buses, run by the IETT, only accept tickets. Private buses accept cash, but bring exact change as bus drivers do not carry any. The cost of one ride is around 1.35TL. The city's main intercity bus terminal is the International Istanbul Bus Station, located in Esenler.
For something a little cheaper, dolmuses are shared taxi-vans. The main dolmus stands are in Taksim, Sirkec, and Aksaray, from which you can reach anywhere in the city. Dolmuses are often more direct than buses and cheaper than taxis.
Note that all public buses, trams, trains, and sea buses accept the AKBIL. There is a refundable 6TL charge for this device, which is much more convenient than buying tokens. Rates are slightly discounted and it can be refilled at booths in all the major stations.