Ouch. May has certainly been painful, what with Mr. Market providing the kind of gyrations best experienced on roller coasters. Don't be distracted, however, by the fact that your portfolio -- at least if it's anything like mine -- has likely taken a hit during the month. Instead, it's time to ...

Shop the market
Indeed, it's precisely when equity prices hit the skids that savvy investors should consider a trip to the stock market. But which aisle to head down?

These days, cheap stocks seem plentiful. MittalSteel (NYSE:MT), Pulte Homes (NYSE:PHM), and Deutsche Telekom (NYSE:DT), for example, all sport sub-10 P/E ratios and prices more than 20% below their respective 52-week highs.

Elsewhere, the racier likes of Starbucks (NASDAQ:SBUX), Apple Computer (NASDAQ:AAPL), Google (NASDAQ:GOOG), and Marvell Technology (NASDAQ:MRVL) -- firms that boast five-year earnings-growth estimates in excess of 20% -- have suffered setbacks during the month that, according to certain reports anyway, is supposed to bring May flowers.

Question the answers
So what's the best way to turn to determine whether, given the market's topsy-turvy ways of late, a stock that looks cheap is really a value or maybe just a value trap?

Excellent question, and the Fool offers a veritable horn of plenty when it comes to helping you make that call. One technique I'm a fan of is discounted cash flow (DCF) analysis. With DCF, you don't rely on easily manipulated earnings reports to gauge a prospective investment's fiscal health; instead, you make the company show you the free cash flow -- i.e., the sum they've taken in from operations minus the amount that's gone out for capital expenditures.

Helpful though it is, DCF is really most appropriate for the market's steady Eddies, and even for firms that strike that profile, I wouldn't recommend that any investor rely on it alone. From corporate management to competitive landscapes, there are just too many other factors that a well-informed investor needs to consider before making a decision to buy or sell a stock.

Question the founders
With that in mind, we've asked Fool founders Tom and David Gardner to participate in a first -- a live "teleseminar" during which they'll share their Foolish wisdom on the art and science of buying and selling.

The teleseminar is 100% free, but it's limited to 1,000 Fools who will be selected at random. If you'd like a chance to be on the call, register by clicking here. Once you've signed up, you'll even have a chance to submit a question for the brothers.

Could yours be the one? Impossible to say, but if these days you find yourself scratching your head over whether it's time to buy or sell, I suspect the information you'll glean from the teleseminar will prove useful indeed.

See you (so to speak) on the call!

Shannon Zimmerman runs point on the Fool's Champion Funds newsletter service, and at the time of publication didn't own any of the securities mentioned above. Mittal is an Inside Value recommendation; Starbucks is a Stock Advisor pick. You can check out the Fool's strict disclosure policy by clicking right here.