When Michael Kahn took over the Shakespeare Theatre in the 1980s, he felt the best way to put the struggling troupe on the map was to open the doors for a day while Stacy Keach and the cast rehearsed “Richard III.”

People lined up for the free event, and Kahn’s company has been doing it ever since. For the current “The Two Gentlemen of Verona,” two seatings were offered, and 300 people showed up for each one.

Open rehearsals, Version 2.0: Last month, Woolly Mammoth skated onto thin ice by announcing a plan to let a limited number of visitors into rehearsals for “Civilization (All You Can Eat)” that they could Tweet about. Playwright Jason Grote hadn’t signed off on the idea, and was more than a little skeptical about letting outsiders into a realm that is generally roped off for artists at work.

As theaters explore new methods of turning people on to the product, spectators are connecting and sometimes finding their way backstage in a number of new ways. “We’re trying to develop a whole toolbox of real or technological tools,” says Miriam Weisfeld, Woolly’s director of artistic development.

Woolly’s “Tweet Up!” scheme was perhaps the most adventuresome and high-tech method of letting outsiders in, but Round House, Forum Theatre, Signature Theatre and Arena Stage are also among the companies opening their doors before opening night.

At Arena and Signature, seminars are the mode. Arena’s Theatre 101 is a $100, eight-session course that allows up to 50 people into everything from design presentations to conversations with the artistic team, culminating in tickets to the show. (The seminar cost is $50 for participants under age 30.) The idea came from Chicago’s Steppenwolf Theatre, where the goal was to show the business of producing new plays.

Arena ran the program for the new dramas “every tongue confess” and “The Book Club Play,” and this spring will offer controlled glimpses of “The Music Man” in a seminar that’s already fully subscribed.

“We’ve found real fascination with how this animal works,” says Artistic Director Molly Smith.

It must be true: Tuition is $300 for Signature Theatre’s “ ‘Brother Russia’ Presents,” which gets students a six-part look at the new musical by John Dempsey and Dana Rowe (”The Witches of Eastwick”). It even includes a Critics Corner after the final dress rehearsal, where participants can critique what they’ve seen.

“That’s not my favorite part,” says Artistic Director Eric Schaeffer, who is directing the show.

Smith and Schaeffer say there’s little or no profit in the seminars (a refinement of donor-attended rehearsals that are widely offered as perks for supporters), but the goal is to get people in, open eyes and build loyalty. “Over four weeks, they become cheerleaders for us,” Schaeffer says. “And they have a stronger appreciation for what it takes to put on a new musical.”

That’s the hope, of course, behind any open rehearsal, an old practice more common among symphonies, dance companies, and in Europe. Even where the access is free, it’s not always clear what this door-opening means for the traditionally vaunted Sacred Space that is the rehearsal hall.

“Letting anybody in the room is always nervous-making,” says Mark Ramont, director of the current “Next Fall” at Round House Theatre. Last month a few visitors were treated to this spectacle: “I got [h]issy with an actor, and he got [h]issy back,” Ramont reports. “You have to focus on the work regardless of who’s in the room.”

Actors sometimes respond to visitors with nerves or despair as they sense disinterest in what’s under construction, according to WSC Avant Bard Artistic Director Christopher Henley. On the other hand, some performers get juiced with energy — which can be a double-edged sword. It’s nice to learn where the laughs are, though one director reports that the sessions can lead to mugging and not much real work getting done.

Certain performers are a big draw: Ed Gero, currently in “Red” at Arena, last season attracted a large number of what Round House staffers call “Ed groupies” for their “Amadeus.” (“They were chewing the scenery,” Ramont says of that cast.) The Shakespeare had to add sessions when Elizabeth Ashley appeared in “Mrs. Warren’s Profession” in 2010, filling Harman Hall twice over.

“That took us by surprise,” says Darby Lunceford, the company’s director of marketing and communications.

On the other hand, football, weather, and intangibles can keep the numbers down. (Freezing rain on a January Friday may be why only two people witnessed Ramont’s brief actor spat.) Even with big crowds, Kahn insists that the rehearsals can be productive. He interacts with the guests, asking what they see and hear.

“It’s rather confidence-building,” Kahn says of the sessions. “I actually love them.”

The common Do’s for open rehearsals: allow the actors time to warm up. Forum Theatre Artistic Director Michael Dove, whose small troupe figures to increase the number of open rehearsals , likes to work for an hour to let the actors “get their heads in the game” before bringing in onlookers. Kahn typically schedules the open rehearsal day as the first day the actors begin to take the stage, but their first hour in the space is closed.

Don’ts include nudity, first stabs at violence, and big emotional scenes. “It’s still sacred space,” says Smith. “The rehearsal room has to be a safe environment.”

So why do it, if there are not hard numbers to quantify how many new patrons this access drives through the turnstiles? Forum Managing Director Julia Harman Cain points to industry conversations that theaters typically only sell about 30 percent of what goes on in their operation, suggesting a stock of “untapped inventory.” She also notes the popularity of process shows on TV and open kitchens in restaurants.

“It’s not something theater made up,” Cain says.

“I don’t feel like we’re caving in to any trends,” Dove adds. “I think we’re looking toward a more inclusive experience. ”

“Let’s pull the curtains down,” Round House Producing Artistic Director Blake Robison says. “Let’s see the wizard on the other side.”

Woolly is keeping all kinds of possibilities on the table as the troupe seeks resonance for its work beyond the stage, according to Weisfeld. “Tweet Up” was the product of an aggressive campaign that involves Woolly’s “claque,” — the French opera term for hired supporters — which Weisfeld describes as “young, diverse, highly engaged ambassadors” for the company. From that claque, Woolly culls a specialized focus group that helps staffers strategize about everything from what groups might have a natural interest in the next show to what ideas and trends might be helpful to the artists.

For Weisfeld, the Twitter matter simply indicates that the theater is still figuring out what connectivity and transparency mean. “It’s not throwing doors open all the time,” she says. “There is such a thing as TMI.” Maintaining privacy and protecting risk is still a big deal, and for any sneak peeks, “We have to make sure that everyone is clear about why we’re opening up this stage of the process, and who we’re opening it up to.”

Downstairs in the glass-walled room where “Civilization” is being rehearsed, the tall black curtains are pulled shut. Nonetheless, Tweet Up! was scheduled to continue through last Thursday’s technical rehearsal and will culminate in this week’s final dress. Upstairs in the offices, Weisfeld says that as Woolly continues to pursue the ideals of transparency and openness, “You can’t be formulaic about what’s right.”