Sure, we all feel like geniuses now, right? We stuck it out -- "it" being the worst economic crisis since the Great Depression -- and have now enjoyed fat and happy double-digit gains ever since the market hit bottom in March.

There's surely more to come, right? Right?!

Survey says ...
Who knows? We Fools pride ourselves not on making market calls, which are a great way to get slapped silly by the market's invisible hand. Rather, we take pride in our fundamental focus. Is a company's market share likely to shrink or grow? Has its management team delivered the goods over the long haul while deftly navigating both up markets and down? And in terms of valuation, does the firm's stock look like a blue-light special or a high-end luxury item?

In my experience, that last element -- valuation -- is often the toughest taco to crack. Some companies never look cheap, after all. Others that appear to be bargains may turn out to be value traps instead. Still, in general terms, one thing remains true: When a company sports moon-shot multiples, there's little opportunity to cushion the blow when the overall market hits the skids or when the company itself blows up.

The higher they fly, the harder they fall
For example, take Research In Motion (NASDAQ:RIMM) and Google. The former has gained 71% year to date, even after factoring in its recent dramatic slide. The latter has increased by some 94%. Yet sneaking a peek at this illustration of recent history should be instructive for folks who currently own either company's shares, as well as Fools who may be considering a purchase.

Could investors have foreseen the slide that chopped at least 50% off each company's value? Perhaps not, but if they'd tuned into each firm's valuation, savvy investors might have dodged a bullet by taking gains, waiting for valuation gravity to work its magic.

Shortly before its 2008 slide began, Research In Motion traded at a level that priced in more than 60 times the previous year's earnings. Google, meanwhile, sported a P/E in the 50s back when we were celebrating New Year's 2008. And while both companies have since recovered, RIMM now trades with a P/E just south of 18, while Google has clawed its way back to roughly 48.

Bottom line: A little valuation discipline can go a long way. When an all-but-inevitable market pullback arrives, highfliers can be sitting ducks -- and future bargains, at least in relative terms.

Good companies. Lousy investments?
Along those same lines -- and following big run-ups year to date -- American Express (NYSE:AXP) and Morgan Stanley (NYSE:MS) could be cruising for proverbial bruisings. That goes double for Southern Copper (NYSE:PCU), with a current P/E hovering above 60 -- well above the company's average over the last half-decade.

Last but not least: Infosys Technologies (NASDAQ:INFY), which is currently priced at more than 20 times analysts' earnings estimates for fiscal year 2010. Given the eternal -- and generally erroneous -- optimism of Wall Street's Gucci-loafer set, not to mention the weakness of the American consumer, that's way too rich for my blood.

That's particularly true, moreover, when there are plenty of long-haul overachievers trading on the cheap. Cases in point: IBM (NYSE:IBM) and Pfizer (NYSE:PFE), both of which trade with P/E's below the S&P's and their own five-year averages to boot.

The Foolish bottom line
There's more to uncovering values than just parsing price multiples. Separating truly cheap stocks from merely cheap-looking ones is a full-time job.

If you'd like some assistance when it comes to avoiding value traps, be sure to check out the Fool's Inside Value service, where the emphasis is squarely on rock-solid companies trading for a song. Click here to take the service for a completely free 30-day test drive.

This article was first published June 2, 2009. It has been updated.

Shannon Zimmerman runs point on the Fool's Ready Made Millionaire and Duke Street services and doesn't own shares of any of the companies mentioned in this article. Google is a Motley Fool Rule Breakers recommendation. American Express and Microsoft are Motley Fool Inside Value picks. Motley Fool Options recommends diagonal calls on Microsoft. The Fool has a strict disclosure policy.