The summer before I went off to college, I took a crazy job selling books. Not at Barnes & Noble, mind you -- door to door. Every June, this company ships college students off to faraway cities where they learn how to sell the old-fashioned way: by pounding the pavement, ringing door bells, and making a pitch for homework-help guides aimed at kids of all ages. The job's attraction is that if you can average "only" 3-4 sales per day, you can wind up making something like $14,000 in a summer. I was struck clueless by the dollar signs, so I of course signed right up.

My destination was Macon, Ga., where I worked 14-hour days in 100-degree heat, six days a week. While I didn't get too many doors slammed in my face (Georgians are way too nice for that), I did get a whole lot of no-thank-yous. According to my sales manager, however, I actually wasn't getting enough nos!

You see, I was averaging about 14 houses per hour and 13.5 nos, when what I needed was something closer to 20 houses per hour and 19.0 nos. According to the sales math, only by knocking on 20 doors each hour would I be on pace to sit down and talk to one person per hour, or 14 per day. And only by giving my pitch (i.e., begging) 14 times a day would I have a shot at landing the requisite 3-4 sales.

As it turned out, I never for the life of me could get to 20 doors per hour (probably too much hanging out and drinking lemonade at non-buying, but friendly households). Consequently, I didn't get my 3-4 sales per day. But I did learn a valuable lesson: Success at certain activities in life boils down to a simple numbers game.

I tell you that story because I think there's a parallel to investing. When it comes to stock picking, the numbers game at work is one of knowing as many companies as possible. Obviously you have a life and various time constraints, but the more stocks you know -- and I mean really know -- the better equipped you are to fill your portfolio with winners.

Really knowing a company means reading its 10-K, proxy, recent earnings reports, news releases, message boards, and anything else that helps you grow familiar with its business and the people running it. (Some good sources for this info are Fool Quotes & Data and Yahoo! Finance.) If you don't have time to do this kind of research on your own, you may want to consider a subscription investment research publication, such as our own The Motley Fool Select, which offers three fresh stock ideas per month, each one fleshed out in-depth, plus updates on past picks. We also offer The Motley Fool Stock Advisor, which is David and Tom Gardner's monthly investment newsletter.

But whether you do your own original research or read published stock ideas, the principle is the same: The more companies you know, the better prepared you will be to make optimal portfolio selections. And given that this market trades at a not-so-cheap 19.4 times earnings (as measured by the S&P 500), you'll probably need to look all the harder to find values here in 2003. Recently, for example, in choosing my stock recommendation for the January edition of Select, I researched four candidates that looked attractive on the surface (low P/Es, good brands, long-standing franchises), out of which only one proved to have solid value.

I expect that beating the market this year will require more stock-picking savvy than during any of the last three years. But no matter what direction the market takes, there will always be undervalued stocks to be ferreted out. It's just a matter of playing the numbers game and looking at as many promising companies as possible.

That's why my No. 1 investing New Year's resolution is to take an in-depth look at one new stock idea every day. To the extent I succeed in sticking to this discipline, I intend to use my online articles here to share my research. Along the way, we'll no doubt need to discard a number of stocks that don't measure up for one reason or another. But hopefully in doing so, we'll also together find some of 2003's eventual winners that are out there waiting for us among the market's 9,000 publicly traded companies.

First up tomorrow is a promising little sweater maker that sells for only 5.9 times earnings.

Matt Richey is a senior analyst for The Motley Fool. He appreciates your feedback (MattR@fool.com). For his best Foolish stock ideas and in-depth analysis that you won't find anywhere else each month, check out our newsletter, The Motley Fool Select. The Motley Fool is investors writing for investors.