It's the two-year birthday of our most recent bull market -- or as I like to call it, El Toro Loco ("the crazy bull"). While I hate to rain on this toddler's birthday parade, I think our current bull market's too irrational to last much longer. Now more than ever, investors should pack their portfolios with the strongest, most well-run companies they can find.  Thankfully, I've discovered one potential advantage to make that search a whole lot easier.

Putting the "bull" in "bull market"?
What's made this bovine so ebulliently bonkers? After all, unemployment's still high, and our economy remains awash with "discouraged" and underemployed workers. Commodity price spikes in food and gas squeeze consumers' discretionary income. No matter how you slice that data, our overall economic health looks shaky at best.

Have any of the major problems that got us into this mess improved in the last two years? It's difficult to make that argument. The housing market's still a mess; Bank of America (NYSE: BAC) recently put nearly half of its mortgages into what it called a "bad bank structure."

Many companies either languish in bankruptcy protection already, or face with that dire possibility. Dynegy (NYSE: DYN) just said today that it could be forced to file for bankruptcy protection if it can't meet the earnings targets its creditors require. Borders recently filed for a high-profile bankruptcy, and consumer-facing companies like Uno Chicago Grill, Fuddruckers, and Sbarro also face similar financial difficulties.

Some pundits already rumble that our economy needs the Federal Reserve to step in with more quantitative easing -- fondly dubbed QE3. Either way, that should take some of the steaming, snorting bravado out of this crazy bull's charge, since the previous round of quantitative easing was already unprecedented.

Ignore the bull, search for the best
The demented bull market boosted many stock prices over the last two years, whether they deserved the bump or not. If we stop getting a bull market, and start getting its horns, overvalued stocks could fall harder and faster than most.

Smart investors simply need to take strong business operations into consideration and avoid speculative bubble buying right now. To seek out more robust companies, consider those with strong rankings in corporate governance and social responsibility screens.

Plenty of organizations screen for "good" companies that score high on environmental sustainability, positive impacts on communities, and other benevolent acts.  Corporate Responsibility Magazine recently released its annual list of "100 Best Corporate Citizens," which ranks large companies according to their policies on the environment, climate change, human rights, employee relations, corporate governance, philanthropy, and financial responsibility. Johnson Controls (NYSE: JCI), Campbell Soup, and IBM (NYSE: IBM) won the magazine's top three "best" corporate citizen slots this year.

However, such rankings can be subjective and controversial. Altria Group (NYSE: MO), one of the least likely candidates for most people's "best corporate citizens" list, ranked surprisingly high at No. 35. In addition, despite the repeated recalls of consumer products that have tarnished its reputation, Johnson & Johnson (NYSE: JNJ) still ranked No. 20 on the list (with a cautionary Yellow Card acknowledging the issue).

Bear in mind that in recent years, Corporate Responsibility's methods for building the list changed, gearing the rankings toward extremely large companies. Previously, it often included smaller, far more pure-play "good corporate citizens," such as 2006 winner Green Mountain Coffee Roasters (Nasdaq: GMCR). This year, Green Mountain didn't even make the list.

Put safety first
However you define them, strong, stable stocks will leave you better prepared to ride out a market stampede. Running with the bulls is exciting while everybody's still standing, but getting trampled by El Toro Loco could prove a painful experience indeed.

Check back at every Wednesday and Friday for Alyce Lomax's columns on corporate governance.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.