Here are some things you should pay attention to, during your stay in Istanbul:
Even though you are supposed to be able to drink tap water, no one does. You can find really cheap bottles of water all over the city. The taste is much better and of course it is healthier. As for brushing your teeth or cooking, tap water is perfectly safe!
Cats and Dogs
There are thousands of cats in the streets of the city. Turks love cats, so you may see them at the most weird places. Prepare yourself if you suffer from allergy
Street food is one of the best things about Istanbul. It’s everywhere, it’s cheap and tasty! In general it is pretty safe to enjoy street food but there are two types of them which may cause trouble: midye dolma and kokoreç. Both of them should be eaten in clean and safe places so please ask your hotel or the locals for advice on where you can eat them
Turks love to smoke! So if you are a non-smoker you should have patience sometimes. There is nothing you can do about it… so this is something like warning. The positive is that smoking is not allowed in closed spaces