Well, as a start, you haven't seen Istanbul if you haven't been to Taksim. The covered bazaar, the bosphorus, the mosques, the museums, they're all wonderful sites to see. But Taksim is where the city's heart beats. It's like the Champs Elysees of Paris, or the Times Square of New York. The region between the Taksim Square and Tunnel, with Istiklal Caddesi (a car-banned avenue) starting at the former and ending at the latter, is the jewel center of interest in Istanbul. You can find anything here: Trendy shops, local cuisine servers, theaters, hundreds-years-old apartments, pubs, businessmen, prostitutes, couples in romance, homeless kids-anything you can dream of. If Istanbul is a woman, Taksim is her face.
Quick Tips:
1. Keep your money in a safe place, and don't expose a large amount of it outdoors. Istanbul isn't a specially dangerous place, but wealth is low and you really don't need to provoke the 'street people'.
2. Open your eyes! Istanbul is most probably quite different than any other city you've seen. Strange sights are common, and you don't want to miss any of it. Check out abandoned-looking historic buildings, the friendly people who are always willing to interact with foreigners, the amazing souvenirs, and the lively 'underground' life at Taksim.
3. And a final quick tip: Do bargain whenever you buy something that hasn't a price tag on it. And you can still bargain for things with price tags, excluding obvious things like newspapers, cigarettes, beer, maps, etc.Best Way To Get Around:
Public transport is very cheap in Istanbul, but the buses are almost always crowded (and I mean crowded!) and somewhat dangerous for foreigners; pickpocketing or sexual abuse are not uncommon. If you are not on a tight budget, taxis are the most comfortable way of transport though make sure the driver turns on the fare-meter when you get on and it reads 'gunduz' at day and not 'gece', which is the night fare, and more expensive. 'Dolmus', which are usually vans, are a good solution if you're not that rich. They work on the most used routes and are considerably cheaper than taxis, though more expensive than buses. Walking for moderate distances is strongly advised: Breathe the city! And two last remarks:
1. Don't rent a car! The traffic is extremely chaotic, especially for a European or North American.
2. Use the maritime boats when crossing the Bosphorus! You'll most probably get stuck in jams if you take a wheeled form of transport. And the breeze of the Bosphorus is a must to be experienced.