One thing that everyone can agree on is the value of a good guide. After I fruitlessly searched through a variety of Web sites that specialize in booking guides and tours, the guide that I ultimately found—through Viamigo.com—was the worst of both trips. Viamigo promises to "connect [travelers] with professional guides and local cognoscenti." A search of its Costa Rican experts yielded a curious array of options, such as the "sophisticated and charming gentleman" in San José. (Was he advertising his services as a guide or an escort?) I e?mailed the three most promising candidates and heard back from just one: Pablo Gonsalves of Nature Adventures Tours. Gonsalves agreed to take me on a tour of Manuel Antonio National Park, and then gave me the name of another guide for Monteverde. Things looked promising—until Gonsalves stood me up. When I called him half an hour after our arranged meeting time, he wasn't apologetic and, more bizarre, told me that I'd be happy when I learned why he was late: A romantic tryst had taken him out of town, and he hadn't bothered to look at his appointment book upon his return. Gonsalves's lack of professionalism soured me on the entire experience—and he did not volunteer to refund any of the $50 fee. To add insult to injury, when my travel companion offered him a novel she'd just finished, Gonsalves admitted that he hadn't read a book since high school. Not exactly the thirst for learning I expect in a guide.

Gonsalves did do one thing right, though: The guide he recommended for Monteverde was terrific. Danilo Brenes, who was waiting for me at the preserve's gates when I arrived 20 minutes early, proved to be friendly, charming, and knowledgeable—in short, a model guide. But what impressed me most was his palpable enthusiasm. It was as if each bird, monkey, and insect were the first he'd ever spotted, and yet he'd been guiding in Monteverde for almost 20 years. Even though Brenes is one of just 23 guides certified by the Monteverde Cloud Forest Preserve, he wasn't listed on any of the Web sites that purport to connect travelers with guides. I eventually tracked him down on ¡Viva! Monteverde's site (monteverde-online.com), which is run by a network of local businesses.

Although Edwards's guides didn't quite match Brenes in terms of passion, they were as knowledgeable about their areas of expertise as Brenes was about his—and they had more impressive résumés: Julio Madriz, who accompanied me for the first three days of my trip, is a university professor and Nature Conservancy researcher when not guiding; José Calvo, my guide in Manuel Antonio, works primarily for Lindblad Expeditions and has lectured to Audubon groups in the United States. In the future, I will never book a guide without a recommendation from someone I trust (like a travel agent or a friend). Credentials are important, but the way a guide interacts with his or her audience is the surest measure of skill.