What companies are tomorrow's big winners? In our ongoing series, I'm chatting with Fool analysts and advisors to find out the stocks they're watching and the catalysts that would signal it's time to buy. Today, Motley Fool Alpha and Big Short analyst Matt Argersinger shares two companies on his watchlist and one he just bought for himself. (For your convenience, you can now create your own version at MyWatchlist.com, your free customized hub to follow the performance and Fool coverage of the companies you care about.)

Two companies looking for traction
If you've had a Sam Adams beer in the past week, you're doing your part to support the investment thesis that would vault Boston Beer (NYSE: SAM) from Matt's watchlist to his portfolio. The company is a favorite of his, with a strong and growing brand, a charismatic and successful founder/chairman, and an intelligent business model. By opening a new plant in Pennsylvania two years ago, Boston Beer was able to at least partially solve the craft brewers' dilemma: breaking out of its regional market while retaining its image as a quality beer.

Unfortunately, the market noticed that it was able to successfully double its capacity, and the share price has soared during 2010 as a result. But if Sam Adams becomes a true national brand, Matt sees a huge upside from here. So he's keeping an eye on the stock price and market share, while diligently tasting the beer on a regular basis to make sure quality isn't being sacrificed by growth.

At first glance, EnerNOC (Nasdaq: ENOC) sounds like a business model that was drawn up after quite a few rounds of Sam Adams. The company gives its equipment to its customers and then pays them for using it. But there's actually a very cool -- and very successful -- business model at play.

EnerNOC is the leader in the emerging field of demand response, helping to fuel the smart grid. Basically, EnerNOC has a network of customer sites, from office buildings to supermarkets to industrial sites, that it has hooked up with its monitoring technology, allowing it to keep a real-time eye on each customer's energy use. By allowing its customers to turn down their power usage when they don't need it, EnerNOC gets paid by utility companies and grid operators for freeing up the power, and it passes along a portion of that cash to its customers. As Matt said, "It's free money for the companies that sign up."

While the strategy is innovative and revenue has jumped 10-fold since 2006, the business is only now on track to post its first annual profit in 2010. Its first-mover status could well give it a sustainable advantage in this new market, especially if it can lock in increasing numbers of long-term contracts, but it also might just point the way for giants like Honeywell (NYSE: HON) and Johnson Controls (NYSE: JCI). If EnerNOC maintains its hold as the key player in this area, we're looking at a big-time multi-bagger for years to come. Matt's a bit too conservative an investor to take a risk on a rule-breaking company still in its relative infancy, but he's definitely going to be watching for signs it will survive to adulthood.

One to promote from the watchlist
Many Fools believe natural gas is cheap, trading about the same price it did in late 2008. And they believe it's not going to stay that way forever. Matt was definitely on that boat and specifically was keeping an eye on Ultra Petroleum (NYSE: UPL) as a way to capitalize on that market inequity. The natural gas exploration and production company has a relatively cheap valuation and is very efficient. So, after keeping the company on his watchlist for months, he was pleased to get confirmation of his interest when Motley Fool Special Ops made the company a recommendation. As soon as trading guidelines allowed, Matt made a purchase.

And that's exactly why it pays to watch. You can make smarter investing decisions with your own version of My Watchlist, new and free from the Fool. Click below to start following one of the stocks mentioned above:

•     Add Boston Beer to My Watchlist 

•     Add EnerNOC to My Watchlist

•     Add Ultra Petroleum to My Watchlist

Roger Friedman doesn't own shares of any companies mentioned, but they're all now on his watchlist. EnerNOC is a Motley Fool Rule Breakers pick. Boston Beer is a Motley Fool Stock Advisor selection. The Fool owns shares of Ultra Petroleum. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.