The shoeshine trick and the "let's have a drink" invitation

Near Sultanahmet and Taksim, a shoeshine man may "drop" his brush in front of you; pick it up and he'll insist on shining your shoes, then demand a large fee. Walk past it. The other classic: a friendly stranger invites you to a bar for a drink, and the bill arrives at hundreds of dollars with large men by the door. Politely decline invitations from strangers to unnamed bars, and you'll have no trouble; Istanbul is otherwise a welcoming city.