DC Capital Striders, a Meetup running group, nears the end of a run that started and ended at the Smithsonian Metro station. The group is not about training marathon runners; it has more of a laid-back vibe. (Katherine Frey/The Washington Post)

Washington is not, by any means, an easy place to find your social circle. The mix of newcomers, workaholics and far-out suburbanites makes it hard to meet anyone, much less make plans to hang out over the weekend.

So for one week late last month, I made my own plans.

I went Meetup mad. I logged a nearly five-mile run in the shadow of the monuments, took a lesson from veteran salsa dancers in the subtle art of working it, shed my usual heels and hit the hiking trails — I even rode a party bus — all with complete strangers. With my little experiment, I’d intended to prove that I could fill my calendar with meetup after meetup, but with it came an altogether different result: With each outing, I grew more confident; I could fly solo and have a great time doing it.

Meetup.com was launched 10 years ago in New York in the wake of the Sept. 11 terrorist attacks. An open invitation to defy the instinct to hide out in our homes, it gave mommies and rock climbers and techsters a way to find one another outside of chat rooms and instead plan play dates, expeditions and happy hours. “Every Meetup,” co-founder Scott Heiferman wrote in an e-mail to users last month, “starts with people simply saying hello to neighbors.”

In Washington, described so often as a “transient city” that one wonders if it isn’t printed on all plane tickets to Reagan National Airport, the most frequented Meetup gatherings are social ones, revolving around networking, making friends or bringing together singles. With such a thriving Meetup community — the sixth most active in the nation — it’s possible to scratch just about any itch, whether you’re a geography buff (for whom there is the GeoNerds DC Meetup), a Francophile (try the very active DC French Meetup) or simply slay at board games (see: VA/DC Social Boardgame Meetup). Often, it’s as easy as searching for an interest, clicking to RSVP and then showing up — and not only is it acceptable to arrive solo, it’s the norm.

A salsa Meetup event at Cuba Libre on Ninth Street NW. (Evy Mages/For The Washington Post)

“Meetup lends itself to people coming out on their own, without having the need to drag someone along,” says J.T. Yaung, a lead organizer in the area’s most populous Meetup group, the 20s & 30s Going Out Group.

Yaung’s group — one of the five I visited in my meetup-filled week — draws a mix of singles and classic transients, 20-somethings who have landed their first big job in a new city (or are looking). But others attract an in­cred­ibly diverse mix of people, ranging from longtime locals rethinking their social circles as their friends couple up to empty-nesters trying new hobbies.

What follows is the lowdown on how some of the area’s most popular Meetups groups have managed to help people find their niche.

“The stories — people getting married, people finding great buddies — it’s so uplifting,” says Kellie Carlisle, who in 2007 founded the Mid-Atlantic Hiking Group and has since seen the group transform into a network of thousands of outdoors enthusiasts. “That’s the story of Meetup. We don’t have little cliques to shut people out.”

20s & 30s Going Out Group

The title gets the point across: The largest Meetup group in the Washington area caters to the young and the upwardly mobile. Oldsters need not apply.

(Lisa Schreiber/The Washington Post)

There’s a logic behind this, of course. The Meetup, founded in 2005, attracts people at a certain point in their lives: A large chunk of the active members are new to the area, on their own again after youthful long-term relationships, living out in the ’burbs or working with colleagues decades older.

I meet all of the above at the first meetup in my little experiment, a night of club-hopping on a party bus. The night’s organizer, J.T. Yaung, came to Meetup in 2007, throwing himself into a Chinese language group, a supper club and the 20s and 30s group. An uber-organizer, he launched the popular local Meetup 20s & 30s Asian Going Out Group (and he runs the 30s & 40s group, too); for each, there are picnics and charity happy hours, volunteer outings and tubing trips. The party-bussers on this night get not only the giant white chariot to drive them to such clubs as Ultrabar and Muse, but they also get VIP treatment and drink specials (which the group members, who paid $35 each for the night, take full advantage of).

Meetup “has been a godsend,” says Simone Carpenter of McLean, a first-timer with the group. “In Oregon,” she tells me, “I had family. I had friends. I was that really shy, quiet person. Moving out here, I had to take the initiative.” Like many Meetup members, she joined a half-dozen groups at once. “I had to get out there,” she says. “Otherwise, I’d be sitting at home.” It was at the Baking Bliss Meetup that she met Dana E. Popp, a firecracker from Philadelphia. At Muse, the pair dance up a storm with their newfound crew, their bracelets creating one green blur in the darkness.

“How else are you going to meet people?” Popp asks. “Meetup is so easy. There’s no reason you shouldn’t do it.”

Sign up: www.20sand30sgroup.com

DC Capital Striders

Google “running group in D.C.” and the fates will guide you to the DC Capital Striders, a loose caravan of a running club that regularly clocks five-mile runs around the region. The group launched in 2006 with a weekly run, not to transform members into marathon runners but to “take advantage of what Washington, D.C., had to offer,” says founder Rick Amernick.

The Striders maintain that laid-back attitude to this day. When I show up on the Mall for the weekly, post-work dash around the monuments, the group is warmly receiving new members and welcoming back old ones who all but vanished during the muggy summer.

We set off not far from Smithsonian Castle. I’m no longer much of a runner, but once I reach the 14th Street bridge, I realize I want to cross it. And then I want to cross the broad expanse of Memorial Bridge, too. I quickly find a group that runs at a similar pace and finish the 4.3-mile trek at dusk, with another runner by my side.

“People come to these runs, and they realize it’s a very nurturing group,” says Lauren Modeen, a longtime member. Where other groups “were much more competitive and people didn’t talk to each other, this was a much more supportive group.”

It doesn’t take much to start; show up dressed for a run, stretch and go. The group provides consistency for those who want it. Barry Creech of Arlington started running only in 2008, not expecting to run a marathon. “When I hooked up with the running group, I realized I could,” he says, because it provided a way to train, five-mile run by five-mile run. (Capital Striders also arranges fitness seminars and has hosted a handful of 8Ks.) Within a year, Creech had completed two marathons.

After our run, the sweaty group makes its way to Chef Geoff’s for burgers and beer. Dan Weiser, the leader of the popular Mall run, recalls that he once couldn’t make it around the block. These days, he’s an eight-minute-mile kind of guy.

How do you know, I ask Weiser, if running is for you? “You put one foot in front of the other,” he offers. “If you like it, you’re a runner.”

Sign up: www.meetup.com/dccapitalstriders and www.meetup.com/dccapitalstriders-nova

The Weekly Dinner

Dining out with 20 strangers is a lot like finding yourself at the singles table at a wedding: You can embrace your dinner companions as new friends, or fixate on your gnocchi till you can make a run for the door.

The Weekly Dinner is built on the idea that it’s far better to choose the former — sup with strangers at great restaurants, and perhaps great bonds will follow. The formula has since 2005 brought together an ethnically diverse set of both singles and couples, people ranging from their 20s to their 60s, newcomers and natives; the reservations are almost always full.

The group has developed a reputation for being welcoming, Matt Rizzo, one of the group’s leaders and a longtime member, tells me when I join the Weekly Dinner at New Heights in Woodley Park, because “many people are in the same boat as you. Everyone remembers their first time.”

Members share stories about a visit to Rasika before getting a table there was an exercise in futility; this year, they’ve already hit America Eats Tavern, Ardeo + Bardeo and several other restaurants on everyone’s lips. But the Meetup also spares foodies the stares that come with solo dining. “Even the waitress or waiter will treat you like you’re pitiful,” says Weekly Dinner regular Chu-Ling Yu of the District, who joined because her friends didn’t share her passion for fine food.

The logistics involved in planning one dinner for 20, much less 52 such dinners a year, would give anyone gray hairs; over the years, the six organizers have developed firm rules: Dividing the group into smaller tables works best, both for conversation and for bill-splitting (the group eschews separate checks); no uninvited guests; and any member who racks up two no-shows gets the boot.

Despite those formalities, after the initial awkwardness of digging into the bread basket with strangers — who will make the first carb joke? — the group is warm. Some of the diners are foodies; they gush over the succulence of the duck breast and share bites of their cardamom-scented beignets. But others spend the dinner discussing home towns, favorite restaurants, work and the foibles of becoming a Washingtonian.

“Whatever the mix of ingredients is,” Rizzo says, “it works.”

Sign up: www.meetup.com/theweeklydinner

Mid-Atlantic Hiking Group

It’s a wet, humid morning when I arrive at Scott’s Run Nature Preserve for a four-mile hike with Mid-Atlantic Hiking. Having never hiked, I’m fretting about the appropriateness of my ripped jeans and Nikes, so I’m relieved when I scan the gathering crowd and find that no one is intimidatingly outdoorsy.

Founder Kellie Carlisle launched Mid-Atlantic Hiking in 2007, not long after she moved to the area from Florida. She wasn’t used to the woods, but she wanted to give hiking a shot. “I would go out with other groups, and I’d get left behind, and I’d be terrified,” she says. It’s no wonder that one of Mid-Atlantic Hiking’s mantras is “Leave no hiker behind.”

The group is one of the most active in the area, with 500 hikes a year on average from Pennsylvania to West Virginia. My hike was closer-in, in McLean, and one of the easier trails that the club will traverse. A mix of folk turned out, including a professor nearing retirement, a couple new to the area and young women getting in some exercise. When we head out, we zip quickly up a dirt trail, past hemlocks, ferns and logs. As we begin to climb, the group slows to take in views and the forest’s little surprises, including stream crossings, until finally, we reach a waterfall. “I could never have come to this point myself,” Ling Wu of Gaithersburg says as we peek out over a narrow ledge that offers an obstructed view of the swollen Potomac below. “They know what they’re doing.”

The group makes the unusual move of charging hikers, typically $1 per hike, which most members pay ahead of time through Amazon.com. The fee, Carlisle explains, helps offset the costs of training hike leaders for medical emergencies (and ensures fewer no-shows).

Fall is a great time to check out the trails with the group, which is beginning to crank up the hikes to accommodate the hikers who come out for cool weather and prime leaf-peeping. Or wait till December, when Mid-Atlantic Hiking hosts one of its most popular events, a Monuments in the Moonlight hike on the Mall.

Sign up: www.midatlantichiking.com

DC Salsa Meetup

A Meetup that’s perhaps harder to crack than most is DC Salsa, mostly because rhythm seems to be the minimum requirement. Lucky for me, when I arrive at Cuba Libre on Ninth Street NW with a serious case of two left feet, DC Salsa’s salseros are more than willing to offer up lessons in salsa, cha cha or samba.

“In the salsa community, everybody’s goal is to grow the community,” explains Cathy Freeman, one of the Meetup’s organizers. “They know it’s in their best interest to engage people and get them to come back. People say, ‘I remember being a beginner. Do you want to dance?’ ”

But salsa, Wole Moses of Fairfax explains as he shows me some moves, is also a chauvinist’s dance; if you’re a woman, say yes, don’t worry about where to step and just follow the man’s lead.

The group, whose membership is predominantly beginner and intermediate dancers, flits from small salsa clubs to ballrooms where lessons are frequently offered (get to events early for lessons). On average, the club hosts 10 events a month, mostly on weeknights, because salseros are dedicated dancers, so much so that they don’t cut into dancing time to hit the bar.

At Cuba Libre, the restaurant is packed, and outside the line stretches around the building till well past midnight. The music flits from salsa to clubbier beats, and the Meetup members, wearing little black dresses or slim black shirts and pants for the night, break it down on the dance floor. In the back, I find the pros — the dancers whose bodies whirl effortlessly and whose feet step in sync. For me, watching them might be the best part of the night.

Getting to their level, Freeman tells me afterward, is “all about just committing yourself. You’re going to want to come out, and commit to it, and do all it takes. But it’s an awesome ride.”

Sign up: www.meetup.com/salsa-162