All else being equal, the return you'll earn on any investment comes down to two main things: the length of time you hold it and the price you pay. Of course, every Fool knows that when it comes to investing, all else isn't equal. Nonetheless, those two points are well worth bearing in mind as you go about the business of stock shopping for fun and profit.

They're particularly true, I'd argue, when it comes to the question of price.

Why so?
Most of us, after all, at least intend to be buy-to-hold types when we stake out a position in a stock we like. Alas, our "like" sometimes becomes a full-blown romance, and we fall in love with a stock's story and let emotion cloud our judgment when it comes to assessing valuations and growth prospects.

Google is a classic example. Don't get me wrong: I love it, too, and I use the search service a gazillion times a day at least. And while I'm not exactly an early adopter when Google rolls out new bells and whistles, there are a few to which I've taken a shine. I've been having a blast with Google Scholar, for instance, which is a great way to see what academics in myriad fields are up to these days. The finance service seems impressive, too, and while I won't be chucking Outlook anytime soon, Google Calendar ain't too shabby, either.

Still, fan though I am, I wouldn't touch Google's shares -- not at a price-to-earnings ratio above 40.

Why not?
When it comes to investing in individual stocks, I'm a big fan of companies whose intrinsic value clocks in considerably greater than their stock prices. Beyond that, I also like firms with lengthy track records of generating plenty of free cash flow (FCF) -- cash from operations minus capital expenditures.

On that front, Google's FCF track record is too short -- particularly when the market boasts the likes of Marathon Oil (NYSE:MRO), Baxter International (NYSE:BAX), and Illinois Tool Works (NYSE:ITW) -- which have cranked out gobs of FCF over the course of many years. That's also true of Emerson Electric (NYSE:EMR).

Admittedly, those names don't have quite as much sex appeal as Google. But if that's the profile you're after, you could always consider the likes of Texas Instruments (NYSE:TXN) and Harley-Davidson (NYSE:HOG) -- two more of the market's proven cash generators that also have a bit more "brand."

Why are you waiting?
Just because a company makes it through a set of quantitative screens, that doesn't mean it's a slam-dunk investment. There's more to ferreting out value than just number crunching. That's why I'm a big fan of my colleague Philip Durell's Inside Value newsletter service.

Each month, Philip whittles down the investment universe to just those companies that meet his stringent quantitative requirements and measure up when it comes to more qualitative factors (such as managerial acumen and a laser-like focus on creating value for shareholders).

Shall we dance?
If that sounds like a compelling strategic two-step, I encourage you to take Inside Value for a test drive. It won't cost a thing for a full 30 days, a stretch of time you can use to read through Philip's complete list of recommendations, every inch of financial advice he's offered subscribers, and the service's members-only discussion boards, too.

Whether you take me up on the offer or not, your portfolio will be much better off if you learn how to pick great investments from the ranks of the market's great companies.

This article was originally published on Aug. 5, 2006. It has been updated.

Shannon Zimmerman runs point on the Fool's Champion Funds newsletter service and co-pilots Motley Fool Green Light. He does not own shares of any company mentioned. You can check out the Fool's strict disclosure policy by clicking right here.