A few months ago, I was standing, overlooking the famous Rio Grande River in Big Bend National Park when I had an investing “a-ha” moment. Let me explain…

As the chief-strategist behind Stock of the Month, I get to pick one — and only one — stock a month to add to my “real-money” portfolio. When I notice a major trend developing, I only get one chance to capitalize on it. If my pick doesn’t perform, then too bad — I missed my chance.

That said, for the past several months I’ve struggled to find the single-best investment opportunity to profit from what I think will be one of the biggest trends in the coming year — the rising flow of consumer spending.

It may seem counterintuitive… but believe it or not, even with slowing world growth and high unemployment here at home — U.S. consumers continue to spend.

The chart on the right tells the story…

For the past several months, U.S. retail sales have steadily risen. November’s retail sales numbers were just revised up 0.1% to a 0.4% monthly gain. Meanwhile, sales rose yet again in December, marking the sixth straight monthly increase.

Sales surged even higher during the holiday season. In 2011, Christmas sales were up nearly 5% from the year before…

While these numbers aren’t astounding, they’re still a testament to consumer resiliency. And to make retail even more appealing, if economic conditions continue to improve, then the retail sector should benefit from tremendous upside potential as well.

But even though sales are rising, it’s a little tricky to pick retail winners. Costs for manufacturers have been high and margins have been compressed.

I conducted dozens of stock screens and scoured company financial reports, hoping to find a strong product brand of retailer that I felt could do well.

But it wasn’t until I was hiking down into the Boquillas Canyon, thousands of miles from my office that it came to me in an “a-ha” moment…

As I stood over the flowing Rio Grande River I thought, instead of betting on any individual consumer sector or product, I could profit from the “flow” of consumer spending…

That’s exactly what Visa (NYSE: V), one of my top stocks for 2012 does.

Every time you pay for something with a debit or credit card, chances are Visa is profiting from your purchase. The payment processing sector is dominated by just a few players, and Visa is the largest. Transactions made with Visa account for more than 60% of the world’s market share.

Roughly 45% of Visa’s revenue come from overseas. Visa’s fastest-growing areas are the emerging economies in Latin America and Asia. This can be a challenging area, as more of the population is unserved or underserved by large banks — traditional issuers of Visa’s cards.

That’s probably why Visa recently announced a new mobile payment product for 12 developing countries. The product will enable financial institutions and mobile network operators to offer Visa prepaid accounts for consumers to access through their mobile phones.

Visa also understands that payment processing is evolving in the developed world. It wants to be part of the growing number of people who are looking for new ways to make person-to-person payments or access a payment processor through a myriad of devices, including their phones and tablets.

To expedite these new payment platforms, Visa has opened a new development center, allowing outside companies an opportunity to develop new tools and applications that can be offered to Visa users.

In the quarter ended Sept.30, 2011, Visa’s profits rose by 14% in comparison with the same period the year before. Visa processed roughly 13 billion transactions in the quarter, up 9% from last year.

Action to Take — > So as we look into the coming year, I think Visa could be a smart play. Even though the world’s economies have yet to see a robust recovery, consumer spending is strong and growing.

Rather than try to sort through the retail winners and losers, the simplest and surest way to profit from this strong trend is with the company that profits from the vast majority of credit and debit-card purchase.