I have moved from Istanbul to Ankara several months ago. I love Ankara. Its calmer, cheaper, more arranged and peaceful. However i miss sth. which you can not live in anywhere but Istanbul. Here is my list...Hope it also works as a suggestion list.
Route 1: Pass through Uskudar from Eminonu or Besiktas with boat. Be free while u are continentlessly...Sing and smoke alone on the bottom of the boat.
Have a long walk on the European coast of Bosphorus. Route 2: Emirgan-Yeniköy-Tarabya-Kireçburnu-Sarıyer-Rumeli Kavağı. Take a taxi here - Rumeli Feneri (Enjoy the view in the daylight)
Route 3: Emirgan-Balta Limanı-Bebek-Arnavutköy-Kuru Çeşme-Ortaköy (Reach Orakoy after the evening have a rest on the bench Order a Kumpir and tea)
Route 4: Ortaköy-Beşiktaş-Dolmabahçe-Kabataş-Tophane (Be a part of the city on the wide banquette in the middle of crowded trafic and hight walls of Çırağan and Dolmabahçe Palace, Kabatas Boys High School and Galatasaray University. Find the place that you can touch the waters of Bosphorus in Kabataş 
Order a Nargile in Tophane
Route 5: Kabataş-Cihangir-Taksim-İstiklal Street (You will get tired while you climb the steps but it worths to feel the older and elegance city. Order a coffee in Cihangir. Reach İstiklal on the sunset. Find Halvetia and eat extra delicious home made foods. Choose three different foods in one plate -same price- than Enjoy the night of İstiklal)
Route 6: Galata Tower-Karakoy-Galata Bridge-Eminönü-Gülhane-Sultanahmet-Beyazıt (See how human destroys a city while u look from Galata Tower, Eat fish in Karakoy, See the guys who catch fish in Galata Bridge and think that they are the luckiest residents of İstanbul, Go to Egyptian bazaar in Eminonü and understand what commerce is, Feel the calmness and simplicity in Topkapı Palace say "as dreaded as simple" Let someone disturb you in Sultanahmet becouse it worths to sit between Hagia Sophia and Sultanahmet Mosques. Try to feel the entellectual background and history of the city. Witness a Friday in Fetih Mosque and visit Süleymaniye Mosque.
Route 7: Eminonu to Eyüp bu boat and walk to Pierre Loti. Feel the holyness of the city in Eyüp Sultan Square and mosque go there on Ramazan and see a Teravih prayer and especially morning prayer.
Route 8: Bosphorus tour by boat. Dont pay a lot just take the Municipalities boat. The same tour. Eat yogurt in Kanlıca drink old version of Yedigun. See the wonderful waterside residents. Sit on a bench in Çengelköy and feel like you are in the middle of the sea while you are on the land. And my favourite. Kuzguncuk. Very very little. Just sit there and turn back to your soul. Have 500 metres walk on İcadiye street and see a catholic an orthodox church, a synagogue and a mosque in peace on the same street. Fibd the restaurant which is famous with its cheese. BTW dont go after 500 m becouse upper sides of the street is full of dogs. Pass to Rumeli Hisarı from Anadolu Hisarı with the little wooden boat. Have a rest in Paşa Limanı.
Route 9: Tour of islands. Bicycle or Horse Car tour in Heybeliada.
Route 10: Join a trekking group and have a mountain walk from Kulindağ to Polonezköy. Enjoy the wonderful breakfast in the middle of the nature in Kulindağ and explore Polonezkoy at the end. See how they keep far away from the chaos of the city.
There are some more routes howrver its enough for now. What about your favourite´s in İstanbul?
I wish to visit Istanbul because it a beautiful city i was watching it on TV on the decumentary
