Six things I'd recommend from my experience, if you'd like to believe me.
1) Put your guidebooks away and hire an official guide to take you around. They whisk you past all the queues and provide historical and local knowledge. This can be arranged with your hotel's concierge. They're worth it.
2) Get cleaned up like a Sultan in a Hammam.
3) Detox and drink as much pomegranate juice as possible. They're cheap and ordinary in the side of the world. Drink hot apple tea. It's like cider, but tea.
4) Eat Baklava from Hafiz Moustafa. It rocked my world.
5) Beware of hand-embroidered Turkish textiles. Make sure they're color-fast and will not bleed when you wash it at home. I learned the hard and expensive way.
6) P.S. You can buy Turkish towels from Amazon. You can buy any exotic spice from Kalustyans.