Where to live
Downtown Istanbul is basically divided in three parts, because of the rivers. In the East, there is Sultanahmet which is the historical quarter; in the North, there is Beyoğlu with the famous Taksim Square; and in the West, on the Asian side, there is Kadıköy.
Kadıköy is a great place to be, with lots of restaurants and bars and way less touristy than the other neighborhoods. And it also costs way cheaper on Airbnb!
Transportation stays easy thanks to all the available boats at the Kadıköy pier (e.g. every 20 minutes to Eminonü/Sultanahmet).
Where to eat
Çiya in Kadıköy: it is slightly touristy but is also one of locals' favorites. Delicious cold mezzes (sold by weight) and hot side dishes and kebab.
Kadı Nimet Balıkçısı in Kadıköy: really good fish restaurant hidden right in the middle of the fish market. Try out the Karides Tereyağlı (shrimp in butter) as hot appetizer!
Where to have a drink
Go on Kadife Sokak in Kadıköy (or as they call it, Barlar Sokak which means Bar Street) at night and enjoy a beer. Apparently, one of the best bars of the street is Karga but I have never been able to find it...
Still in Kadıköy, there is a pub called Zeplin. Lots of people at night, and huge selection of international beer!
There are a few rooftop bars, especially in Beyoğlu, with a nice view on the city. I went to the Gradiva Hotel, which was right next to the Karaköy pier, and although it was nice enough I am pretty sure it is not the best option out there.
What to do during the day
Should I even mention the classics? Hagia Sophia, Blue Mosque, Basilica Cistern and Topkapı Palace in the Sultanahmet quarter, Taksim Square in Beyoğlu.
Less classic things (although still quite touristy of course):
- Take a long walk in Kadıköy and go down to Moda and its nice waterfront.
- Go to the hamam, for example at the Aziziye Hamam in Kadıköy. It is quite cheap (40 TL for entrance and scrub/massage) but even though they have a nice English website, be aware that nobody speaks English there!
- Go to Princes' Islands, by taking a boat from Kadıköy. There are a few boats a day. I have never been able to get there though, since I was on the boat on quite a stormy day and the captain decided to go back after ten minutes at sea.
You definitely want to buy a Istanbulkart for transportation. It is around 10 TL and will greatly facilitates your trips throughout the city (and will even allow you to use public restrooms!)
Do not go to western-like malls in Istanbul, it is really not worth wasting your time. The prices are the same as in France, in my case, and the stores are exactly the same as well.