Istanbul is doubtless the pounding heart of Turkey, but there are some things about this vibrant city, that can really drive you crazy.
1. Don't go to the Sultanahmet-district after you're done with the Sightseeing
The good thing is that the Ottomans build nearly all the highly recommended Sightseeing-spots in walking distance. The bad thing is that the Turks know it and try to earn as much money as possible. So go there, make the tour, pay the high entrance fees, try to recognize as many different languages as you can and then don´t come back. And don't ever go to one of the restaurants or bars there, the prices are way too high and you won't meet locals.
2. Some advice for the Ladies. . .
You might not want to hear it, maybe not believe it, but it is the way it is: When the Turks see a pretty girl with a dress or skirt on, they're not as cautious as the Germans or as charming as the Italians, no, the Turks start to stare. And it's not a little glance, but a strip-off along with some fantasies you don't want to imagine. That's why Turkish girls always act so bitchy! So girls, for your own sake and comfort, dress not as open as you're used to and don't ever walk home alone at night.
3. Don't walk in the streets with a drink in your hand
The Turkish people like to drink, but they have their areas to get drunk. Whether it's in a nice club or a bar, at home or in the Turkish version of a pub, the “Meyhane", no one will say a word. Also in the tourist areas and nightlife-spots like Sultanahmet and Beyoglu it is not a problem. But with some people and districts being more religious than others you might offend them by doing so.
DirtCheapIstanbul.com is a travel guide which shows you how to enjoy a cheap holiday in Istanbul . There's also a list of typical tourist traps and things to avoid.