Istanbul is the world's top travel destination according to TripAdvisor's 2014 Traveler's Choice awards. It's also a very large city of more than 2,000 square miles and somewhere in the realm of 14.1 million people.
The Bosporus Strait separates Istanbul's western (European) side from its eastern (Asian) side. If you stay within close proximity to the Strait, you'll find that Asia and Europe are easily traversed by a cheap and quick ferry ride. Here's that to see and to (the abridged version) on each side:
If you're a first-time traveler to Istanbul, you'll most likely want to find accommodations on the European side, which contains many of the top tourist attractions. There's the Grand Bazaar, which is a maze of stalls and vendors selling everything from ceramics to kebabs to rugs. You'll also see the spires of the rival religious structures—the Blue Mosque and the Hagia Sophia, which are both open to the public. The European side also contains the crush of humanity on Istiklal Caddesi, a pedestrian avenue flanked by shops, restaurants, and nightclubs. Several million people walk this street on any given weekend.
When it comes to finding a hotel, you might want to book in Sultanahmet, Beyoglu, or Taksim Square, which are popular and centralized areas to land. Karakoy is another interesting place: You can pick up fresh squeezed juices and simit, the Turkish bagel, in this waterfront neighborhood where famed Istanbul writer Orhan Pahmuk got his first bike as a child.
Also note that Istanbul's Ataturk Airport, the city's main airport, is located just 15 miles from the European city center. But as you might imagine in a city with this many people, rush hour can be a real beast, so give yourself extra time to get there.
If you want a peek into a perhaps more authentic Istanbulite life, you might want to base your vacation on the Asian side. It's a little less geared to tourists and more to the locals that live there. Here, you'll find vibrant markets such as the ones in the Kadikoy district. There's also an elegant shopping street called Bagdat Caddesi and some great views of the city from atop Camlica Hill. Just south of the Kadikoy district is the Moda neighborhood. Located right on the water, this is a great place for a cup of Turkish çay tea or an Efes beer and some people-watching. You'll also come across restaurants that Asian-side inhabitants frequent like Çiya Sofras, a restaurant highly praised by New Yorker writer, Elif Batuman.
As for airports, this side contains Sabiha Goçken, which was built in order to relieve some of the overwhelming traffic that the Istanbul Ataturk airport was facing. This airport is about 20 miles from Kadikoy, and you'll find that many low-cost carriers land here.