A great tour guide can make a holiday. They will add colour, context and a sense of how what you're seeing fits into a much bigger picture; they'll answer your questions and direct your attention towards details you might not otherwise have spotted. They should also know just when to be quiet and let the experience speak for itself, according to Sam Ham, a professor of communication psychology at the University of Idaho who also specialises in training guides and has worked with the Abu Dhabi Tourism Authority. Although a good guide should share stories, Prof Ham says that it was a moment of silence that had the greatest effect on him when he visited Bali.
He and his wife had been travelling with a fantastic guide - "he asked questions rather than just giving out information, which meant he was able to direct us towards things he knew would interest us" - who suggested that they attend a funeral service.
"Funerals are public in Bali. The whole community comes out to see it." Before joining the funeral their guide explained its importance in Balinese culture, the religious significance of the ceremonies involved and the correct etiquette. "Then he stepped between my wife and I so that we looked like his friends rather than his customers and we stood silently at the funeral. It was one of the most moving and truly amazing experiences of my life."
By keeping silent and allowing the Hams to observe the funeral as members of the community rather than outsiders observing another culture, the guide allowed them to understand the experience emotionally as well as intellectually, Prof Ham says.
Of course, good guides also need to get the basics right, he adds: a thorough understanding of their subject; fluency in the travellers' language; and an ability to tell compelling stories. "Guiding is not just giving entertaining facts to pleasure seekers," he says. "The guide's role is to provoke the tourists to think, to immerse themselves in the story and to make their own meanings with respect to the things the guide shows and tells them."
Some people, eager to get the best out of their holiday with a cultural twist, turn to travel companies that offer specialist lecturers - often academics - as well as professional local guides. "At an archaeological site anyone can point and say this is a bath, that is the Eastern gate," says Irenie Ekkeshis, the sales and marketing director of Traveller, an independent company with strong ties to the British Museum. "You can get that from a guidebook. But a lecturer will say 'right, picture this' and will tell you the story of what happened in that bath and why, or which invaders entered through that gate, and what the implications were."
They should also be able to answer questions that deviate from the standard script - something that local site guides may not be able, or even allowed, to do.
Sometimes lecturer-led tours can also offer access to sites that are not open to the general visitor, Ekkeshis says. "For example, the lecturer who does our Easter Island tours is Dr Jo Anne Van Tilburg. She's a world-renowned authority on the Easter Island statues and has done the most [academic] work on the island in the past 20 years." The archaeologist, who splits her time between UCLA and Rapa Nui, is the director of the Easter Island Statue Project, which means that she can offer her groups access to working digs that aren't open to the general public.
While expertise, storytelling ability and general good humour make for an excellent companion, a bad guide can be something of a nightmare: unfriendly, inflexible, unable to answer questions and - in some cases, at least - the purveyors of entirely untrue stories. Andrew Appleyard, who worked as an archaeologist in the Middle East before joining travel operator Exodus as the international sales manager and an occasional guide, is often amused by the "facts" he hears at some historical sites.
"The guides have clearly learnt something and they say that each time. It's blatantly wrong from the outset, but to them it's gospel truth," he says.
Urban myths abound and many "original" historic sites are actually restorations. "You say, no there's no way that's original - that column is upside down, that building isn't on its foundation and that one is actually sitting on a modern concrete plinth," Appleyard says.
Gill Charlton, a British travel writer, gets particularly frustrated with guides who are so full of facts and figures that they want to impart that they can't tell when their audience would rather have some peace and quiet. "I've been on tours with excellent guides who really know their stuff but who never shut up," she says. "It's incredibly irritating."
Better guides, however, appreciate that people need time to form their own impressions - they don't want to have someone do all their thinking for them. That's one of the reasons that academics leading tours will often give a talk the evening before visiting a particular place; this gives people enough information to put things into context and to avoid missing interesting details without overwhelming them on the day.
Tehran-based Saeed Alizadeh, an author who frequently guides for Martin Randall Travel (MRT), wishes more travellers understood just how hard professional guides work and how seriously they take their jobs. It's not simply a matter of pointing out attractions and adding commentary; he puts in weeks of preparation around everything from accommodation to road closures for every trip, on top of the extensive reading and research that he does to stay on top of the latest history and archaeology, for example. Tourists should help their guide do his or her job by being polite, punctual and showing courtesy to both guide and fellow guests, he says.
Getting the best out of a guide is sometimes down to you, says Jane Taylor, a Jordan-based writer, photographer and MRT guide. While most of the company's clients are well prepared, she has come across some tourists who have not done even the most basic research into the cultural mores of their hosts. "It amazes me that some women will wear the most décolleté things, which even I don't find aesthetic and which people here find very offensive. You will not get the best out of a country if you try to impose your values on it."
With more and more of us researching and organising the minutiae of our trips online, it's not surprising that some travellers eschew formal tours in favour of finding a guide independently. Websites such as www.ourexplorer.com list scores of local guides, although anyone planning to hire a guide this way should always ask for references rather than simply relying on online reviews. People who have plenty of time and are not travelling in the high season might be able to find someone when they arrive simply by keeping their ear to the ground; this approach has the advantage of allowing you to meet your guide before making up your mind. However, be aware that good guides are often booked up well in advance, often by big tour operators.
It's also worth meeting potential guides at your hotel for an interview before agreeing to hire them. "You have to like the person, because that will make a big difference to how much you like your trip," says Maan Al-Sabbagh, a professional guide based in Syria. "If you don't feel comfortable with your guide, you have the right to say something and ask them to find someone else."