Meet inside Coffeetopia Eminönü cafe, next to the Eminönü Ferry terminal·. It is centrally located next to the old historic quarter of Istanbul. It's easily reachable by tram, taxi, or walking.
The tour ends at Karaköy - Eminönü Vapur Iskelesi pier on the Asian side. Your guide can assist you with directions in case you want to stay longer in Kadıköy, or take a boat and transport back to your accommodation (in Taksim or Eminönü/Sultanahmet).