I think the first question to ask is if you need a tour guide.  I think it is a good idea to hire a private or group guide to get an orientation of a city or to get in-depth knowledge of an attraction or site of particular interest.

For example, I recently gave travel advice to a couple who will be in Florence, Italy for a week.   I recommended hiring a private guide to give them an overview of the city.   They hired her for half a day and according to the travelers, she made all the difference in the world.  The guide oriented them to the city, gave pointers on what and when to visit certain attractions, let them on to special events going on in Florence, and tipped them off on great places to eat and relax.

In another case, I gave travel advice to friends going to Paris to see their daughter who lives and works there.   She’s the perfect tour guide for them in Paris.  But they wanted to do a weekend to go to Bayeux and see the Normandy Invasion Beaches.   I recommended and excellent tour company that brings small groups (up to 8 people) on a full day tour of the beaches and surrounding area.  The tour company’s expert knowledge and experience was far better (and less expensive) than the travelers renting a car and finding their way over 30 miles of beaches, museums, and memorials.

When we go to Peru, guides are very inexpensive, maybe $60 for a day.   We like to hire a guide to take us up to the Sun Gate or perhaps to the Gardens of Mandor.   We find the local guides point out things we would never see on our own.

When I go to London, I like to join one of the famous “London Walks”.   It only costs about 8-12 pounds to get on a tour with 20 or so people on interesting walks such as “The Jack the Ripper Walk”, “Old Town London Walk”, or “The British Museum Walk”.   Socializing with other travelers is another benefit.

Finding a good guide is straightforward.  

• Find someone who speaks your language well.
• If possible, find someone who comes highly recommended.  TripAdvisor is a great source.  Most European cities have agencies or travel information centers that can help with guides.
• Set the price BEFORE the tour begins.  A word of warning, some European private guides can get 300-400 euros for a full day tour.
• When looking to engage a guide, if he/she starts telling you what you want to do, find another guide.  A good guide will listen to you, make suggestions, but ultimately does the tour itinerary you want.
• This might seem unusual, but in Europe I like guides who are originally from the United States.  Why?  Well, they speak English well and for most of them, they visited the city where they are guiding originally as a tourist.  I think they have a better feel for what a traveler is looking for.