The listed consultants will add enough value to justify their cost only on certain types of trips. So you must first determine whether you're better off using their services or making the arrangements yourself. Generally speaking, if you have more money than time, hire one; if you have more time than money, don't.

Do Hire a Pro For...
•Start-to-finish customized itineraries with all the bells and whistles
•Once-in-a-lifetime splurges (e.g., wedding anniversaries) involving four- or five-star hotels
•English-speaking guides and drivers
•Special access to monuments, events, or people
•Cruises with private shore excursions

Don't Hire a Pro For...
•The cheapest options
•Airline tickets only
•Single components of a trip (e.g., a one-day tour, restaurant reservations)
•B&Bs or run-of-the-mill hotels (such as those of a mid-priced chain)
•Redeeming frequent-flier miles or guest points only