Most hotels have sit-down toilets, but hole-in-the-ground models – with a conventional flush, or a tap and jug – are common. Toilet paper is often unavailable, so keep some with you. Many taps are unmarked and reversed (cold on the left, hot on the right).
In most bathrooms you can flush paper down the toilet, but in some places this may flood the premises. This is the case in much of İstanbul's old city. If you're not sure, play it safe and dispose of the paper in the bin provided. Signs often advise patrons to use the bin. This may seem slightly gross to the uninitiated, but many Turks (as well as people from other Middle Eastern and Asian countries) use a jet spray of water to clean themselves after defecating, applying paper to pat dry. The used paper is thus just damp, rather than soiled.
Public toilets can usually be found at major attractions and transport hubs; most require a payment of around 50 kuruş. In an emergency it's worth remembering that mosques have basic toilets (for both men and women).