(WSJ) - Yes, the free wine tastings are a big draw. But there’s more to winery tours than meets the tongue. Lettie Teague goes behind the scenes at Chateau Ste. Michelle, one of the best-known wineries in the U.S., to find out what really makes a tour tick

MORE THAN a quarter million wine lovers visit Chateau Ste. Michelle in Woodinville, Wash., each year. Quite a few of them take the free tour of the winery, one of the best-known in the country as well as the oldest and largest in Washington state. Some take the tour to learn a little bit about wine production, grape growing and the history of winemaking in Washington, while others do so for the free wine.

The tour is one of the most important features at Chateau Ste. Michelle, according toJoan Fennell, who is in charge of training new tasting-room hires, aka guest services representatives. A former high-school English teacher, she has worked part time at the chateau for over 16 years and is clearly passionate about the place and position.

Ms. Fennell is both admired and feared by her co-workers—admired for her dedication to the chateau and feared for the high standards she holds for her charges. Ms. Fennell has taken guest services reps off tour duty for “not knowing what they’re talking about, talking too fast or not interacting with guests,” she said.

There are currently 69 part-time guest services representatives, and about 30 more are added to their ranks each summer. Every one of them must take three days of training, and “everyone has to give a wine tour,” said Ms. Fennell.

I spent the larger part of a recent weekend with Ms. Fennell and other Chateau Ste. Michelle tasting-room personnel. Although I’ve visited countless tasting rooms all over the world, like most oenophiles, I’d never given much thought to what happens behind the scenes. Chateau Ste. Michelle seemed like a pretty good place to find out more.

The winery is the only one in Washington with a sizable piece of real estate (105 acres) on the western side of the state. Nearly all Washington vineyards—including those owned by Chateau Ste. Michelle—are located in the eastern part of the state, where it is so dry it’s almost arid. The west, where Woodinville is located, half an hour north of Seattle, is considered too rainy for growing grapes. This, by the way, is one of the tour talking points.

There are quite a few talking points in the three-page memo that all employees are expected to memorize, starting with the five tour objectives: “telling the Chateau St. Michelle story,” educating visitors about the state, creating “fond memories,” entertaining visitors and creating future “ambassadors” for the brand.