Exploring Istanbul for the First time: The Ultimate 3-day Guide!
Firstly, let us get you from the airport to the hotel (in this guide I picked out Dalan Hotel, in Fatih district, because it really did not disappoint me as a first time Istanbul visitor/ bed+breakfast+near the metro and tram, what more do you need). But you can also choose any hotel with good reviews in this district or even a Airbnb.
If you are landing on the newest Istanbul airport (İstanbul Havalimanı) then you will go with the metro but first you will buy a Istanbulkart (probably the cheapest transport prices you will ever pay in your life). When you enter the metro, look for a small yellow or blue ATM. Everyone buys their own Istanbulkart from there (it's the third option at the ATM). The latest info is that the price is 50TL, just the card for one person (there is no group card), so about 1,30 euro and everyone tops their card with at least 100TL (about 2,80 euro) onto their card for starters because a single fare is now 20TL.
*The card can be topped up by placing it (the red square on the pic) and waiting for the card to load (do not press anything). Insert the banknotes that the machine accepts (5,10, 20 or more TL) and then press OK. Then wait again until the confirmation sign appears and then take the card. In the same way by placing it you can check how much money you have left on your card (it appears on the screen).
So from the the Istanbul airport you go on the M11 Gayrettepe (you get off here, the last station) and then you continue on the M2 to Yenikapi (also the last station where you get off.
Or from the airport Sabiha Gökçen you take the metro M4 Kadikoy and you get off at Ayrılık Çeşmesi where you take the Marmaray Halkali/Atakoy line to Yenikapi (also like a metro it just connects the two continents, do not worry you will not even feel you are underwater). And from Yenikapi you just walk to the hotel (about 10min). Always when you exit Marmaray there is like a stool machine where people just wave their carts to and walk pass (depending on the distance that you go on the line that is how much refund you could get, so do not be lazy try it).