Appropriate Attire -- In Istanbul, especially in the more modern neighborhoods, female dress is modern, even racy, but when visiting the more traditional neighborhoods in and around the Old City, modesty will at least broadcast a different message to those likely to leer. Male visitors might want to be aware that Turkish men simply don't wear shorts, no matter how hot it gets, so wearing Bermudas or cutoffs will at the very least brand you as a foreigner. Meanwhile, coverage for men and women entering a mosque is naturally more conservative: for women, shoulders, legs, and head must be covered, and men should be sensitive to any skin exposed by shorts or tank tops. It's a nice idea to carry around a scarf, but all mosques provide some type of head covering at the entrance. Also, remember that shoes must come off before entering the mosque.
Cleanliness -- Turks were among the first civilizations to provide water as a public service, illustrating at a basic level how clean this culture is. Even restaurants and hotels will boast of themselves and their kitchens as being hijyenik (hygienic). Public water fountains can be found around town as well as in the entry courtyards to mosques (these are the ablution fountains). Hand washing is a serial activity in Turkey, and where water is scarce, most carry moist towelettes. After meals, it is customary to proffer the open palms of your hands to your waiter when he passes by with a small dispenser of cologne.
Gestures -- Turks are zealous hand shakers, so be prepared for enthusiastic greetings. Remember to proffer the right hand only, as the left hand is considered unclean. Responses to certain questions take some getting used to: Instead of shaking their heads in our familiar "no" gesture, Turks tip their heads slightly backward, raise their eyebrows, and sometimes accompany this gesture with a "tsk" sound. When answering a question posed in the negative, as in, "The Grand Bazaar isn't open today?" the Turkish response will be "yes" in confirmation that you are correct. Certain hand gestures that would almost never be performed by a non-Turk are considered rude. For example, two gestures have sexual connotations. The first is a closed fist with the thumb protruding between the pointer and middle fingers. The second is slapping a closed fist. Now, forget I told you this.
Gifts -- If you've been invited as a guest to someone's home, it goes without saying that you mustn't show up empty-handed. Some nice chocolates are a good option (choose ones that are alcohol free if you don't know how religiously observant the family is), or you can bring flowers. If you've been invited to a restaurant, it's always good form to offer to pay (although no matter how forcefully you try, you'll lose).
Avoiding Offense -- The adage that "sticks and stones may break your bones, but names will never hurt you" has no parallel in Turkey, because in this culture, words hurt. Sarcasm can be easily misinterpreted, meaning that you could insult someone without even realizing it. Topics that are generally sensitive include human rights, the Kurdish issue, the Armenian question, and anything to do with the movie Midnight Express. At the same time, Turkish people are quite interested and open to discussing these things, so just be sure to find a balance. Also, when seated (usually on the floor), pointing the sole of your foot at another person is considered an insult. When bargaining for anything, once you've agreed on a final price and shaken hands, the deal is done. Changing your mind at the last minute or reneging on the deal is the surest way to piss off your carpet salesman (or other merchant); but in my opinion, all's fair in love, war, and commerce, particularly in Istanbul.
Photography In some places, photographing state buildings or military and police installations is forbidden. Taking video or photographs in a museum is often prohibited (a picture of a camera with an "X" through it will be posted around the building); where photography is permitted in museums, there is customarily an additional fee to be paid when purchasing your admission ticket. Also, it is generally advisable to get a subject's permission before photographing them. As a rule, women in chadors (the head-to-toe black robe) do not wish to be photographed under any circumstances.
Note: This information was accurate when it was published, but can change without notice. Please be sure to confirm all rates and details directly with the companies in question before planning your trip.