Twitter represents a gold mine of marketing possibilities, but the vast majority of firms haven’t figured out how to transform those 140-character tweets into sales.

One exception is mega-brand Dunkin’ Donuts, which has started to track dollars flowing from Twitter by tallying the number of people who click through from a “Win Free Coffee for a Year Offer” on Twitter. Users who enroll in the “DD Perks” program are entered into a company database. The company has a quantitative value for database members, although it will not disclose that number or the Twitter click-through rate.

Yet while Dunkin’ has become a dominant brand on Twitter with over 46,000 followers, most firms are in the early stages of puzzling out how best to monetize a website whose passionate users crank out an average of 50 million tweets each day.

Still, a growing number of companies are seeking out Twitter for marketing purposes: 35 percent or 173 of Fortune 500 companies have active Twitter accounts, according to a recent study about corporate Twitter usage in 2009 from the University of Massachusetts Dartmouth Center for Marketing Research. The study called company growth on Twitter “explosive.”

A relatively early adopter of Twitter, David “Dunkin’ Dave” Puner has been tweeting for the chain since October 2008. Puner tweets about deals on coffee, munchkins, and breakfast sandwiches, the company’s “create your own donut contest,” and also replies to dozens of requests and comments daily.

Puner notes that Dunkin’s irreverent brand personality lends itself to Twitter and looks to its thousands of followers as proof that the company’s time spent tweeting is worth something. Although Puner notes Dunkin’ is still “figuring out Twitter,” he also said: “It’s a great place to get that real-time feedback and to find out what consumers want from you as a brand.”

Still, the majority of companies are somewhat clueless about Twitter’s business impact. Corporate Twitter strategies are “all over the map” ranging from hyper-engaged companies skilled at building trust with followers down to firms that play it safe, sending out lackluster tidbits of information, said Emily Riley, analyst and research director at Forrester Research Inc.

“In truth, relatively few companies are doing any of this well,” said Riley in an email.

But companies like Staples Inc., which has a “Tweet team” of five staffers and has amassed more than 31,000 followers, are passionate about mastering the art of "microblogging." The company started using the site late last year and tweets mainly about deals and customer service.

Even at a sophisticated company, figuring out the ROI of social media “is the million-dollar question,” said Michelle Ormes, Staples’ director of corporate branding. “Right now...we value the number of our followers and how engaged they are.”

Business-to-business firms are also placing increased importance on social media and Twitter. Forrester predicts that B-to-B firms will increase spending on social media from a total of $11 million in 2009 to $54 million in 2014.

A prime example is EMC Corp., which, with more than 3,777 followers, views Twitter as a valid channel for one-on-one customer conversations. And with 400-plus EMC employees with personal Twitter accounts monitoring mentions of the technology company, there’s plenty of opportunity for that back-and-forth. While the company has chatted on Twitter with potential customers, according to EMC’s director of digital strategy Len Devanna, the company doesn’t use the channel for sales.

“But I’d be lying if I said sales wasn’t on our radar,” said Devanna.

Small businesses have also found followers, although dubious proof of sales, on Twitter. Somerville, Massachusetts-based Kickasscupcakes owner Sara Ross has attracted more than 800 followers and tries to give her cupcake fans behind-the-scene glimpses of her business by posting videos. But, Ross thinks her Mini Cooper, which is decked out with her store’s branding, has gotten her the best free publicity.

Not all companies are convinced that tweeting is a necessity, even ones that believe in social media. Car-sharing firm Zipcar has some 30,000 fans on Facebook, but does not actively tweet, although company spokeswoman Nancy Scott says the company “listens” on Twitter. Zipcar’s inactive Twitter page has close to 1,000 followers.

While many companies are still simply engaging with followers on Twitter, Mike Schneider, digital chief at Watertown, Massachusetts-based Allen & Gerritsen, says his agency encourages clients to use Twitter as part of larger marketing strategies. Corporate social-media strategies that are only focused on engagement are “shortsighted,” said Schneider. “If you push, we feel like you can ask for permission to sell something.”

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Lisa van der Pool is a staff writer for the Boston Business Journal.

Learn how Dunkin Donuts and others have been utilizing Twitter.