Any good investor is bound to pick up good habits from other good investors. It's no different for me, though I confess that labeling me with the moniker "good investor" may be stretching things a bit. Still, one of the neat things I first picked up from Peter Lynch in the investing classic One Up On Wall Street was to buy what you know. Then I watched how Motley Fool Rule Breakers chief analyst and Fool co-founder David Gardner refined that notion to buy what you buy. (That is, invest in companies whose products you love so much that you buy them repeatedly.)

Both are extremely powerful ideas; ways to screen for stocks simply by embracing a little intellectual curiosity. Yet both ideas can also be improved, as I found out yesterday in browsing Amazon (NASDAQ:AMZN) for a little research and Christmas shopping. (Shhhh! Don't tell my wife!)

You see, Amazon has this neat feature called "Top Sellers," which, naturally, displays the site's best selling products by category. Presumably, this is for the discerning consumer who wants to know what handy new items are available. Or for the shallow and selfish consumer who's desperate to keep up with the Joneses. Either way, it's a very cool idea, and a helpful tool for the alert investor. How so? Amazon reports that 43 million Americans shopped at its site in November, up 6% from the same period a year ago.

That's a lot of sales. Heck, with those numbers, Amazon is at least as good an e-commerce benchmark as Wal-Mart (NYSE:WMT) is a retail benchmark, even if Wall Street takes Sam Walton's superstores a little too seriously. But the point here is that bestsellers in that kind of volume should lead to higher profits. And higher profits usually lead to better stock prices. Follow me? Good. Now, let's check the toy department. Here are Amazon's top five sellers as of this writing:

  • V-Smile from VTech (NQB: VTKHY).
  • LeapStart Learning Table from LeapFrog (NYSE:LF).
  • Fridge Phonics Magnetic Letter Set from LeapFrog.
  • Musini - MagicSensor from Neurosmith.
  • Dora the Explorer: Magic Friends Singing Dora from Fisher-Price, a unit of Motley Fool Inside Value pick Mattel (NYSE:MAT).

Looking at this list, it seems investors ought to expect good things from both VTech and LeapFrog, yet each has struggled. (Indeed, LeapFrog's problems were made all too clear yesterday.) Which, of course, proves this is a purely subjective exercise; more fun than empirical study.

Still, there's a powerful lesson to be learned by what we've done here. For all its inconveniences, holiday shopping is by far the most overlooked and underappreciated opportunity for stock research in the world today. Millions of people, in forking over billions of dollars, are missing rare opportunities to enrich themselves even as they enrich the lives of others. Don't let that happen to you this season.

For related Foolishness:

Amazon is a Motley Fool Stock Advisor recommendation.

Why not take a break from all that Christmas shopping and do your soul some good. Support the Fool's 8th annual Foolanthropy charity drive.

Fool contributor Tim Beyers shops for stocks wherever he thinks he'll find them. Yep, that even includes watching Oprah. Tim doesn't own shares in any of the companies mentioned in this story, though you can get a peek at his portfolio by reading his Fool profile, which is here.