Where is it?
Situated above Cyprus, Turkey is in Eastern Europe.  A direct flight from London to Istanbul is about four hours. 
Where should I be heading for?
For rich culture and history, most definitely Istanbul.  Ankara is the capital but Istanbul is home to the major historical attractions.
Entry requirements:
Check your Turkish consulate in your country for details. For British citizens, your are granted a three month multiple visa on arrival for the sum of £10. Exact money is required.  Make sure your passport has at least three months validity remaining or you may not be admitted.
Health:
No concerns though you are advised to arrange travel insurance (as with any holiday) to cover you.
Top 5 things to do:

1.  Grand Bazaar - the place lives up to its name with over 4000 shops in this remarkably clean in-door market.  It is also the largest souq in the world.  Here you will come across true Turkish hospitality and great souvenirs.  Always make sure you barter - half the fun is bargaining with the chatty vendors.

2.  Spice Bazaar where you will find a gorgeous aroma of spices and ingredients such as saffron, turkish coffee and of course, Turkish Delight.
3.  Take a sight-seeing tour of Istanbul, which covers the Blue Mosque, Aya Sofya (a church-cum-mosque-cum-museum), Süleymaniye Camii (the largest mosque in Istanbul), Hippodrome (no, not that tacky nightclub in Leicester Square! This used to be a chariot racing ground), Topkapi Palace and Dolmabahçe Palace (a symbol of the Ottoman Empire).  Local travel agents and hotels can book you half or full day trips (with lunch included) which start from about £15 per head.  It's strongly advisable to go with a guided tour - they will fill you in with the history quickly and efficiently, and also show you the way to these attractions plus they are good value for money. 

4.  Belly dancing - there are many places offering evenings of belly-dancing and dinner at competitive prices.  I can't speak for all of them but I can certainly recommend the cabaret at Sultana's (about £30 per head).  The food may be average but the show they put on is superb and believe me, when the belly-dancers take to the stage, you won't be sorry that you let your dinner go cold.  
5.  If you're not shy, have a 'Hamam' otherwise known as the famous Turkish steam bath, where you sit and sweat it out in a hot room before being scrubbed by a masseur/masseuse.  There are separate sections for men and women; masseuses for the ladies and masseurs for the gentlemen.  A full session, which lasts 90 minutes costs about £12.

Is it expensive?

The currency (Turkish Lire) takes a while to get your head around - everything is priced in millions.  Visiting a tourist populated city like Istanbul inevitably means paying the price for it but actually, it's not bad at all.  Hotels are very reasonable (four star) and food is cheap.  If you fancy something classy, the prices are very affordable and naturally, the quality is better. 

What's the food like?
Istanbul offers eateries of different qualities so the more you pay, the better quality service and food you will get.  Having said that, the variety of Turkish cuisine available is pretty much the same wherever you go - shish kebabs (skewered pieces of lamb, chicken or beef grilled), kofte (minced lamb grilled), served with rice, vegetables and chips but the more refined restaurants offer more tantalizing dishes.  Highly recommended is the roof-top restaurant of the Seven Hills hotel.  The breath-taking view of the Marmara sea sandwiched between Aya Sofya and the Blue Mosque is a bonus on top of the delicious food.  Another restaurant is Cozy Pub, with a fine menu of steaks, kebabs and generally all things delectably Turkish. The Turks are also very fond of aubergines and peppers so expect lots of stuffed ones on the menu.
Is it safe to drink the water?
Stick to bottled water, which is cheap to buy - about 30 pence for a large bottle from any groceries shop.
What are the toilets like?
Restaurants loos are very clean - the posh ones even have toiletries and pot-pourri.  Owners are usually kind enough to let you nip in if you need to.  
What to wear:
Anything you like, though when you visit places like the Blue Mosque, bare shoulders and legs have to be covered up (especially for the ladies) but don't worry as the mosque have scarves and sheets to hand out. 
Best time to visit:
Between June to September, when the holiday season kicks off and so does the gorgeous sunshine.  
Don't miss:
sampling and bringing back a few boxes of authentic Turkish Delight.  You'll find the real thing here - accept no other.
Most overrated thing:
Turkish rugs.  You will be spoilt for choice as there are hundreds of shops showing off their finest carpets but since the tourism boom, traders have upped the prices to such ridiculous heights that it isn't worth forking out £700 (or higher) for a rug (plus paying duty at HM Customs & Excise on arrival), when you could probably get it for less back home.   
(5/5)

Photos: Afsheen Shaikh

Lonely Planet: Istanbul  Opodo