"I'm all alone," the innovator said to me.

Starting a business can sometimes be so lonely.

Team up with others? Seek success, and be happy.

There must be 50 ways to find co-founders.

Maybe you need to imagine that rhyme as if Paul Simon were singing it, but when I give talks about entrepreneurship, the No. 1 question I'm asked is, "How do I find a co-founder?" Among former liberal arts majors, it's a bit more specific: "How do I find a technical co-founder?"

My most basic advice is simply to tell a lot of people that you're looking for a co-founder, cast a wide net and ultimately team up with someone you trust who has compatible skills (in that order). To dig a bit deeper, however, I reached out to a huge group of successful entrepreneurs for their experiences. I received hundreds of replies. In no particular order, here are 50 of the best ways they told me they found a co-founder.

(Got another idea? Let us know in the comments below.)

1. Friends from college

It worked for the guys at Facebook, and so many others. Take Gautam Gupta and Ken Chen, for example, co-founders of NatureBox, an online snack food service, who met at Babson College, or John Crepezzi and Kenny Katzgrau, who started Broadstreet Ads.

2. Friends from high school

It's another very common story--for example, co-founders Zalmi Duchman and Yos Schwartz, who founded FreshDiet.com in 2006. They got to know each other when they roomed together in boarding school.

3. Friends from kindergarten

Some people get started early. Zach Schau and his co-founders at Pure Fix Cycles met when they were little kids, and "couldn't imagine starting a successful business with anyone else."

4. People you meet over drinks

Switching gears, sometimes you just have to do the legwork. Alison Johnston Rue, CEO of InstaEdu, an online tutoring marketplace, "reached out to and had drinks with dozens and dozens of engineers" before she met Joey Shurtleff, who eventually became her technical co-founder.

5. People you meet over coffee

Dean Wright of Voytech Products, which makes Snack Spout, said he met his eventual co-founders when he overheard them "chatting in my local Starbucks ... about my [area of] expertise: consumer products."

6. Your siblings

That's another common response. For example, twin brothers Sam and Andy Prochazka started Novosbed, a memory foam mattress company. Then, they recruited their sister, Helenka.

7. Your parents

I can imagine this might work differently for different people, but a few talked about starting businesses with their mothers or fathers.

8. Former co-founders in another venture

Granted, this presents a chicken-and-egg problem if you're a first-time founder, but if it's an option, it's worth considering. There's probably no better person to launch with than someone you've started a company with before.

9. Former co-workers

If you've worked together as employees, you might be able to work together as co-founders. I heard from dozens of people with this story, for example Ari Tulla and his co-founder at BetterDoctor.com, who had worked together at Nokia.

10. Your spouse

Sometimes the business comes first, sometimes the romance. Two of the three co-founders of Skin Authority, Celeste and Ted Hilling are married now, but they first met years ago when he saved her from a guy who was hitting on her after she ran a marathon. Or else, there's Guesterly, whose husband-and-wife co-founders came up with their company idea while planning their wedding.

11. Former competitors

If you're watching your competitors, you might find someone worth working with. Co-founders Michael Sterko and Barry Wise, who started KnowEm.com together, met when they were competitors trying to dominate the same SEO terms.

12. Founder dating

This is sort of the rage right now, with quite a number of founder "dating" sites, like FounderDating, Co-FoundersLab and several others.

13. Regular dating

Louisa Eyler and Eric Jackson met on the dating site PlentyofFish in 2009. A few years later, they were running Lock Laces together, which sells elastic, no-tie, bungee performance shoelaces.

14. At school reunions

I've written about this before, but just because you didn't meet your co-founder during school doesn't mean you can't later meet him or her at a school-related event. Go to your reunions.

15. Accelerators

Related to some of the other co-working suggestions, simply applying to a startup accelerator can lead to finding a co-founder. Kevin Leneway and Adam Tratt, co-founders of Haiku Deck, said they met at a Seattle startup accelerator called Techstars. "We joined forces and within weeks we had closed our $600,000 seed round," Tratt told me.

16. At church

Oddly, I don't think any co-founders who contacted me cited meeting each other through religion. It might make sense, though; you probably have some shared values.

17. At meet-ups

Tech Meetups are great places to find co-founders. "Startup events pull in both kinds of people [technical and business-minded]," reminded Nishank Khanna, founder of Bright Journey. "They're a good way to connect to other startup fanatics."

18. Playing sports together

I heard a lot of stories of former teammates working together. Similarly, Lucas Kovalcik and Tim Walsh met through a mutual friend in high school and grew a friendship based on a love of rock climbing. Now they run Gravity Vault, a franchised, indoor rock climbing business.

19. Playing sports against each other

Sam Hodges gave Alex Tonelli a black eye the first time they met, during a Dartmouth-Brown rugby match. Later, they ran into each other at business school at Stanford, started a chain of fitness centers and now run the U.S. business of Funding Circle.

20. Through mutual introductions

This seems like the heart of networking. For example, co-founders David Donner Chait and Chris Davis lived 1300 miles away, but were introduced by a mutual friend and thought they were a perfect match. They launched an online travel planner called Travefy in 2012.

21. Through cold-calls

London-based brothers Nick and Anthony von Christierson quit their finance jobs to build a parenting mobile app, but as unmarried entrepreneurs in their 20s without children, they knew they needed someone more established in the space. They cold-called Dr. Jen Trachtenberg, a nationally recognized pediatrician, and convinced her to join their company, Baby Bundle, which launches next month.

22. Through pure chutzpa

Art Booppanon walked up to Nick Warnock, who had been a contestant on The Apprentice, after a speaking engagement. Years later, the two have launched several products and companies, including the Wellograph wellness watch.

23. Through weekend hackathons

Maybe even better than founder dating--why not team up with strangers and try to build a product or a company in a weekend? At least if you fail, you'll fail fast.

24. On LinkedIn

Here's why LinkedIn can be so important. Cofounders John Steinberg and Scott Hublou of EcoFactor met through the networking site.

25. By entering business plan contests

Maybe you won't leave with a prize, but a partner. Chris Hulls of Life360, an app designed to help keep families connected, met his co-founder Alex Haro as the result of contacts he made at a business plan competition at the University of California, Berkeley.

26. By entering totally nonbusiness contests

Co-founders Brian Estes and Nate McVicker, who came up with an app for police and school emergencies called Hero911, told me they met in a Texas Hold'em tournament.

27. By taking a class

You didn't meet your ideal co-founder during college? Try taking another course in a relevant field, this time with your eyes open for someone great to work with.

28. Your siblings' friends

Who has your back like your siblings do? (If that's a complicated answer, just move on to No. 29.) If your brother or sister trusts someone who has the skills you need, maybe that suggests you'll be able to trust them as well.

29. Former vendors

This worked for Andres Zapata, who started branding and marketing firm idfive with a former vendor, Rob Beal. However, she advised, "Date before you marry. Do a couple of projects together before you make a full commitment."

30. A former boss

If you liked working with each other in a hierarchical arrangement, maybe you can work together as peers.

31. Starting on your own, while you keep looking.

David Morken, CEO of Bandwidth, started his company in 1999 by himself, although he was "literally praying at his desk to find someone that he could work with." He survived, however, and the company now has 300 employees and $160 million in revenue.

32. Family friends

If you're telling family and friends that you're looking for a co-founder, you might find that they're close with someone you never even thought of. Your dad's buddy from crochet class, maybe? Your mom's friend from the rifle range? I'm trying to use unusual examples here; the point is to think broadly and creatively. Who do they know that you should want to know?

33. Online forums

Hey, people can having Internet dating relationships. So why can't they find co-founders this way? Giancarlo Massaro of ViralSweep met his co-founder a decade ago when they were teenagers on a forum called Sitepoint.

34. Going to parties.

Socialize. That's how Desiree Vargas Wrigley and her co-founder Ethan Austin met--at a Super Bowl party. They went on to found GiveForward, which provides "free online fundraising pages allowing friends and family to raise money directly for a loved one" in need.

35. Tapping your network

Michael Ivey said he met his co-founder in Dallas at the suggestion of mutual contacts. "Everyone said we should meet. Three months later we formed Modern Message," he said, although he added, "For you article though, I can't stress the importance of working under pressure with someone BEFORE formalizing a partnership."

36. Hiring an intern

Mike Szymczak started out as Jason Lucash's intern at Major League Soccer in California. When Lucash moved on to take a job at Jansport, he recruited Szymczak to work with him. Years later they started OrigAudio, and they say they're making $5 million a year.

37. Hiring freelancers

If you can envision founding something with a former employee or boss, why not a former freelancer? Scott Barlow, a UK-based salesman, told me he launched a small marketing business with a co-founder named Michal in Serbia, whom he'd first hired as an animator on the freelance site, oDesk.

38. Working in a co-working space

I'm partial to this one, having had a great experience in a co-working space, and I can definitely see how this would work. For example less than a year after Frank Muscarello and Ben Blair started working separately at Chicago startup center 1871, they'd teamed up and launched MarkItx, an online exchange for buying and selling used IT hardware.

39. Running a video ad

This one is unusual, but why not? About seven years ago, Deena Varshavskaya, founder and CEO of Wanelo, posted a four-minute YouTube video looking for a technical co-founder. In truth, it wasn't a successful search, but it did get her a lot of free press.

40. Your friends' college friends

Agnieszka Wilk was also looking for a technical co-founder to help launch her interior design website, Decorilla, and wound up going with the classmate of a friend who had graduated from MIT. "Once he was on board it was much easier recruiting the rest of our technical founding team," she told me.

41. Just start pitching.

Rob Daley and Henry Thorne, co-founders of 4moms, which makes robotic baby gear, teamed up after Thorne pitched the venture capital firm where Daley was working at the time. He didn't get the investment, but he did gain a partner.

42. While traveling abroad

Josh Rosenwald and Jojo Hedaya, the co-founders of Unroll.Me, met during a gap year between high school and college, while they were studying abroad in 2008. Their email-taming system has 700,000 users in two years.

43. With a BFF

Cofounders Scott Hill and Andy Medley of PERQ, a marketing and promotions company that they say did $30 million last year, were college roommates and best friends before getting into their first business, developing sales leads for auto dealerships. Now, I have to ask: Would I still be best friends with my best friends, if I ran a business with them? Hill and Medley suggest it works for them, anyway.

44. Teaming up with a customer

You can turn some of these people-you've-worked-with models around by recruiting a customer. As an example, Dee Dee Shaw had a store called Monkee's in Wilmington, N.C.; a customer named Brenda Maready wound up working with her to establish a franchising system.

45. By volunteering

Co-founders Michael Marshall and Paola Moya didn't meet while they were in school. Instead, they got together when Marshal volunteered to be an advisor for their shared alma mater's architecture program. Impressed by Moya's work, he teamed up with her and launched Marshall Moya Design in Washington.

46. At a trade show

Where better to find someone else interested in your industry than at a trade show? It worked for Melony Miller Bradley, who met her co-founder and launched a marketing consulting firm specializing in the DIY products industry.

47. As a result of your good fashion

When they worked together at Living Social in Washington, Ricky Choi noticed that Phil Moldavski was a pretty snazzy dresser, but that he always wore regular white athletic socks. More than a few sock-related conversations later, their startup Nice Laundry was born.

48. From hiring a professional

A decade ago, when Steve Anderson was struggling with behavior issues with his son, he met therapists James and Janet Lehman. He was so impressed with their results that he convinced them to team up and launch the Total Transformation child behavior improvement program.

49. At industry alumni events

Why not combine that advice about working with fellow industry veterans and alumni events? Co-founders Matt Galligan and Ben Huh of Circa, a mobile news organization, met each other at an alumni event for Techstars.

50. Pitch a columnist for a popular entrepreneurship website.

Hey, why not? I'm always looking for an interesting new venture.