Do you, like most U.S. investors, prefer to stick with U.S. stocks and mutual funds? There are certainly benefits to keeping your investing dollars in the home country -- shareholder reports are in a familiar format, there's no language barrier, and the business conditions and relevant laws are often easier to understand and more straightforward here than abroad.

But by limiting yourself to U.S. investing, you're missing out on about half the world's stocks -- some of which represent tremendous opportunities. Several easy-to-spot global trends are under way right now, and finding the right way to jump on them could provide a huge boost to your retirement portfolio.

Cars and cash
For example: As globalization continues to do its thing, people in developing countries will continue to acquire the means -- and the desire -- to buy things like cars and home appliances that are part and parcel of the developed world's lifestyle. Indian carmaker Tata (NYSE:TTM) is growing by leaps and bounds, and global giants Toyota (NYSE:TM) and General Motors (NYSE:GM) are solidly established in many developing nations, but the smart play on this trend could be Nissan (NASDAQ:NSANY). Nissan has struggled a bit in the U.S. market in recent years, but its sales in developing nations are growing dramatically -- even as its stock price has floundered for much of the last four years. If you had confined your analysis to North America, you'd miss that.

Another trend: banking services. As Fool Bill Mann pointed out last year, products such as home equity lines and asset management services -- things that are old hat here in the U.S. -- are just now starting to come to market in many developing nations, especially India and Brazil. Leading banks in those countries could be spectacular investments for your long-term portfolio, but a U.S.-focused investor might easily miss out on those gains.

Familiar names, new places
Here's another trend that will seem obvious once you read it: the expansion of global names into new markets. This trend isn't necessarily easy to buy -- GM's debt load and lack of focus on fuel-efficient automobiles greatly outshine Buick's status as one of China's hottest current brands, for example. But sometimes, opportunities show up. Consider SK Telecom (NYSE:SKM), the 400-kilo gorilla of the mobile phone business in South Korea, and one of the country's largest and fastest-growing companies.

Never heard of 'em? You will soon. Rumor has it they're looking to break into one of the biggest markets of all -- our own. While the company has denied plans to acquire Sprint Nextel, it's clear that SK's expansion plans won't stop at the Korean border. One way or another, it's safe to say you'll be hearing about them before too long. But again, investors who insist on staying inside U.S. borders will miss out on a great large-cap growth story.

How do you find all these things?
One challenge to the aspiring global investor is that our familiar resources -- MSN's popular stock screeners, Yahoo! Finance, even the Fool to some extent -- are heavily geared to U.S. investors. It's just not as easy for us in the U.S. to follow, say, Brazilian oil giant Petrobras (NYSE:PBR) as it is to follow ExxonMobil (NYSE:XOM), much less to discover the smaller companies that are often the real rocket fuel in a surging portfolio.

With that in mind, the Fool launched the Global Gains newsletter service. World traveler and veteran international businessman Bill Mann leads the Global Gains team, which has a simple mandate: Find value anywhere in the world. Bill and his team recommend two new companies every month that are poised to benefit from global trends. If you're curious, go discover their latest picks! An all-access pass to all their great global recommendations is yours free for 30 days. Enjoy!

This article was originally published on July 17, 2007 and has been updated.

Kristin Graham updated this article, originally written by John Rosevear. She does not own any of the stocks mentioned in this article. Nissan, Tata Motors, and SK Telecom are Global Gains recommendations. The Motley Fool's disclosure policy has a passport filled with stamps from all over the world.