Skyscanner (www.skyscanner.com) is a great newish search engine providing near-comprehensive information on airlines serving your trajectory of choice.
From the United States & Canada -- Turkish Airlines (tel. 800/874-8875; www.turkishairlines.com), American Airlines (tel. 800/433-7300; www.aa.com), and Delta Airlines (tel. 800/221-1212; www.delta.com) offer the only direct nonstop service to Istanbul's Atatürk International Airport (IST) from the United States. Canadians flying to Turkey can now fly direct for the first time on Turkish Airlines, which instituted flights from Toronto to Istanbul in July 2009. These airlines are just the tip of the iceberg, as most major international airlines flying to Istanbul offer flights from North America much too numerous to inventory, either as part of their own network or in partnership with another airline. Choosing one involves a change of planes in the airline's home country hub, but this slight inconvenience is often accompanied by cheaper, more comparable fares.
From the United Kingdom -- The only nonstop service to Istanbul out of London is provided by British Airways (tel. 0845/77-333-77) and Turkish Airlines (tel. 20/7766-9300), which also flies nonstop from Manchester (tel. 161/489-5287).
There are also budget and/or charter airline options. Onur Air, Senlikkoy Mah. Çatal Sok. 3, Florya (tel. 0212/663-9176; www.onurair.com.tr), offers service from several U.K. cities. EasyJet, Academy, Units 5 & 6 Prince Way, London Luton Airport, Luton, Bedfordshire (www.easyjet.com) flies direct to Istanbul's Sabiha Gökçen Airport from Luton and Gatwick Airports. In addition to these flights into Istanbul, a number of airlines offer direct flights to Antalya, Bodrum, Dalaman, and Izmir along the Turkish coast, most (but not all) in summers only. These include British Airways and Thomas Cook, flying year-round from Gatwich to Antalya; British Airways flies into Izmir four times per week, while EasyJet, Monarch Airlines, Thomson Airways, and British Midland fly direct into Dalaman from a number of U.K. cities.
From Australia & New Zealand -- There are numerous choices for connecting flights to Turkey, the most challenging of which will be selecting your preferred connecting country. The following airlines, in partnership with Turkish Airlines, allow you to make the journey with only one plane change:
British Airways (tel. 1300/767-177 in Australia, or 0800/274-847 in New Zealand), Singapore Airlines (tel. 612/9350-0100; www.singaporeair.com), Thai Airways (tel. 1300/651-960; www.thaiair.com), and Emirates Airlines (tel. 1300/303-777 in Australia, or tel. 0508/364-728 in New Zealand; www.emirates.com); Etihad Airlines (tel. 1800/998-995; www.etihadairways.com) will get you from Sydney and Brisbane; additionally Qantas (tel. 13-13-13 in Australia, 64-9/357-8900 in New Zealand; www.qantas.com.au) flies from Brisbane. From Melbourne, single-change flights can be had on Emirates and Etihad Airlines.
From Perth, Emirates Airlines flies direct to Istanbul with a stopover in Dubai, while Cathay Pacific flies in partnership with Turkish. Travel from Adelaide, Canberra, and Darwin requires two or more changes of plane.
From New Zealand, Air New Zealand (tel. 13-24-76; www.airnewzealand.com.au) and Japan Airlines (tel. 1300-525-287; www.jal.com) will both get you out of Auckland, with a change in Osaka onto a Turkish Airlines flight. Wellington and Christchurch both require two plane changes. For the best possible comparisons, visit the popular booking sites www.zuji.com.au, www.bestflights.com.au, www.airfaresflights.com.au, or the old workhorse www.expedia.com.au.
With global warming issues and petrol prices in the stratosphere, driving to Turkey makes bad sense. But some people just insist on the comfort of their own vehicle, so be prepared for the red tape of sorting out multiple transit visas and at least 4 days of hard driving. There are two traditional routes to take: The "northern" one through Belgium, Germany, Austria, Hungary, Romania, and Bulgaria. Or the "southern" one through Belgium, Germany, Austria, and Italy, with a car ferry connection to Turkey. Drivers planning to stay longer than 3 months must have an International Driving Permit (IDP), which also comes in handy in out-of-the-way places where the local police can't decipher your national version. You'll also be required to provide proof of third-party insurance at the Turkish border.
Depending upon your starting point, train travel from Europe may require a number of connections. Direct trains depart daily from Bucharest and Budapest and take about 27 and 40 hours, respectively. Trains also depart daily to Istanbul from Pythion and Thessaloniki in Greece and from Sofia, Bulgaria. For information on the various connections available, visit www.bahn.de.
Remember that it is your responsibility to obtain visas where required (either transit or tourist, depending on your travel plans) for every border that you will cross.
Sirkeci Station (tel. 0212/527-0050) has been serving train passengers arriving (and departing) Istanbul from European cities for well over a century and has served as a model for railway stations throughout central Europe. A tram stop is immediately outside the station entrance, but don't rely on this if you're first arriving, as there is no ticket kiosk at this stop.
Options for arriving into Istanbul by sea are limited. Serving the Black Sea, Ukrferry (www.ukrferry.com) runs a weekly ferry departing Odessa, Ukraine, on Monday, arriving in Istanbul on Wednesday. Istanbul's municipal ferry company, Istanbul Deniz Otobüsleri (www.ido.com.tr) operates fast ferries and seabuses from Bandirma, Bursa (actually, Güzelyali) and Yalova (all on the south coast of the Marmara Sea), as well as from the Marmara and Avsa islands. All of these ferries arrive into Istanbul's Yenikapi ferry terminal. The privately owned consortium now running the defunct Turkish Maritime Lines -- now Denizline (tel. 0212/444-3369; www.denizline.com.tr) -- operates two cruise-type ferries (pool, fitness room, disco, kid's club) between Izmir (Alsancak Ferry Terminal) and Istanbul (Sarayburnu docks, adjacent to Eminönü) departing four times per week at 5:30pm, arriving the following morning at 8:30am.
A number of ferries plying the Mediterranean arrive to ports in Turkey, but then it's up to you to get from the port to Istanbul. Marmara Lines (tel. 39-010/573-1805 in Italy; www.traghettiweb.it) operates service to Çesme (1 hour west of Izmir, along Turkey's Aegean), from Ancona and Brindisi, in Italy, between March and November. Also in summer, ferries provide service between Sochi (visit www.seaport-sochi.ru) on the Russian coast of the Black Sea, and Trabzon, in Turkey. You can also take puddle jumpers between the Greek Islands and Marmaris, Bodrum, and Çesme.