Chances are you weren't happy with your investment returns this decade. That's because the 10 years ended 2009 were the worst-performing decade in the history of the stock market. Stocks in the aughts averaged an inflation-adjusted 3.3% annual decline.

That's bad, but there is a bright side. If you know your stock market history, then you know that just as periods of outperformance are often followed by periods of underperformance (the 1990s was one of the market's best decades), periods of underperformance are often followed by periods of outperformance.

In other words, the next 10 years are likely to be far better than the last.

Don't blow this opportunity
That tailwind will benefit our returns for the next 10 years. And if we play our cards right by taking a long-term view, regularly adding new money to the market, minimizing taxes and transaction costs, reinvesting dividends, and focusing on superior companies, we should be able to look back at the end of 2019 and say that we had a pretty good decade, investing-wise.

But -- and this is important -- if you want to make the next 10 years one of the best investing decades of your life, you might heed the advice of one of the world's top investors and consider a minor strategic shift.

Are you too U.S.-centric?
The recent trend (and one that we should expect to continue) is that U.S. economic growth has slowed. At the same time, however, India is expected grow almost 9% this year and China more than 10%. Yes, those economies have benefited from public-sector stimulus, but the difference between their numbers and our own is so stark that one can't help acknowledging their rosier forward economic outlooks.

Fast-forward a few years, and this will lead to what PIMCO co-chief investment officer Mohammed El-Erian calls a "multipolar world" -- one that is no longer reliant on the U.S. economy to drive growth. This, he told Fortune, is no doubt good for the globe. "Most of us would rather be on a plane with multiple engines," he pointed out.

Yet if you, as an American investor, continue to focus on American stocks -- and American investors are far too exposed to American stocks -- your investment returns over the next decade may end up being as disappointing as those of the past decade. This, El-Erian points out, is the consequence of being "too U.S.-centric in a globalizing world where the center of gravity is shifting."

Do something about it
This is a real and significant risk that all American investors are facing today, but this is where the aforementioned minor strategic shift comes in. El-Erian says that all you have to do is "recognize that the asset allocation of tomorrow is much more global than the asset allocation of yesterday."

Or in plain English: Set aside some time and money this year to buy more foreign stocks.

I know, I know ...
Despite the surging popularity of emerging-market investments, many Americans remain hesitant to own foreign stocks. That's because they don't know these companies and may not feel comfortable evaluating their financial statements or market opportunities.

That's an understandable objection -- but it still shouldn't lead you to blow this opportunity. So let me give you a head start by telling you a few of the stocks we consider a buy at our Motley Fool Global Gains international research service.

Get your pad and paper ready
One is Dr. Reddy's Laboratories (NYSE: RDY), a generic pharmaceutical based in India. It's not only expected to benefit from rapidly rising health care spending in India, but it also recently signed a revenue-sharing partnership with GlaxoSmithKline (NYSE: GSK) in which that big pharma company will help Dr. Reddy's market its products in other fast-growing emerging markets. If you expect both generics and emerging markets to be serious business over the next few years, Dr. Reddy's is your play.

Another name we like is FEMSA (NYSE: FMX), a Mexican consumer-products company that owns a stake in Coca-Cola FEMSA (NYSE: KOF) (which distributes Coke products in Latin America), a Mexican convenience store chain called Oxxo, and a beer business that it recently agreed to sell to Heineken. Not only do we like the prospects for growth in Latin America, but we also like the potential for FEMSA to use proceeds from the Heineken deal to expand Oxxo and potentially consolidate other Latin American beverage distributors such as Andina (NYSE: AKO-A).

But once you buy Dr. Reddy's and FEMSA, you won't want to stop there. Your portfolio needs exposure to international markets not only through multinationals, but also through companies based in important emerging markets as well. So if you'd like further insights into our top picks from around the world, simply sign up to get all of our Global Gains research free for 30 days. Click here to get started -- there's no obligation to subscribe.

This article was first published on Jan. 29, 2010. It has been updated.

Tim Hanson is co-advisor of Motley Fool Global Gains. He owns shares of FEMSA and Andina, which are both Global Gains recommendations. Dr. Reddy's is also a Global Gains pick. The Fool owns shares of GlaxoSmithKline. The Fool has a global disclosure policy.