Deciding on a guide should involve a few checks on reputation and credentials. First, travel agencies in Turkey must be registered with TURSAB, an agency responsible for accrediting and maintaining the standards of Turkish travel services. Most companies will display their TURSAB number on their website to show they are accredited.
Second, guides to historical attractions and museums must complete a three-year university course to qualify as an accredited guide. Once complete, they must wear a photo ID around their neck so government officials can quality-control tourism areas, penalizing those who are not accredited. This degree, however, does not guarantee excellent service, as some guides still fail miserably in entertaining the interests of their guests over the sound of their own voice. Learning who the best guides are through word of mouth or through websites like Tripadvisor.com will go a long way to securing the services of a guide that others have enjoyed.
Like all other services, it pays to shop around to get the best price with the best guide possible. These days, most agencies will advertise their prices online, but custom tours require a quote, as the itinerary and add-ons will differ depending on the number in the group. For cheaper options, opt for walking tours where possible rather than bus tours, simply because you can rub shoulders with locals and avoid long delays in traffic.
Excerpted from the Second Edition of Moon Istanbul & the Turkish Coast.