This article's swaggering headline smacks of exaggeration -- but it's true.

How it happened
Picture it: New Jersey, 1995. Although not then a Motley Fool employee, I was, perhaps like you, an avid reader of Founding Fools David and Tom Gardner occasionally recommended stocks, and one of their recommendations was an online service provider, America Online.

I was still quite new to investing, and I didn't know enough to do much of my own research. But I did have one thing going for me: I was an AOL customer. I used the service every day, and I liked what I saw of its user-friendliness, utility, and potential. So I bought. I snapped up $3,000 worth of shares and hung on.

Over the next several years, the stock went up and down, sometimes significantly -- but I held on. It mostly went up, and it split and split. I remember checking my portfolio regularly -- several times a day! -- to see how rich I was becoming. Near the stock's peak, I had a 70-bagger! My $3,000 investment had turned into $210,000. If it doubled in value only twice more, I'd be (almost) a millionaire! All from a measly $3,000 investment.

Did I sell shares along the ride up? No. (Some of us don't know when to cut our losses.) Did I sell at least some near the top, when my mom told me to? Nope. (That strange thudding sound you hear is me banging my head on my desk. The silence is my mom, biting her tongue.) I held on.

AOL merged with Time Warner in 2001, and for years after that, the stock struggled. I remember when shares were priced in the $70s, but it's a fuzzy memory. They spent years below $20 until relatively recently, and recently they've been in the single digits. I did sell a big chunk of my shares -- in the teens -- when I needed money for a down payment on my house. And I finally got smart -- I sold more shares to diversify into other stocks instead of holding a big chunk of my net worth in a company in which I no longer had faith.

I continue to hold a few shares, though, and despite my inclination to curse my stupidity for not selling earlier, I'm still sitting on a handsome profit, even at current levels. My cost basis is ridiculously low, and this has still been one of my best investments ever. I shouldn't complain.

How you can do it
If any part of this story appeals to you, know that you have a chance to make it yours -- perhaps with a happier ending -- if you make a few decisions differently. (You might end up as an accidental billionaire!)

Buy what you know
First, pay attention to products and services you know, use, and love -- especially if you see more and more people using them. There may be a great stock behind them, and knowing their products or services will go a long way toward understanding the business. Plenty of well-known companies have done phenomenally well over the past decade or two -- let's look at a few.

Do you use TD Ameritrade (NASDAQ:AMTD) as your brokerage? Do you occasionally pump gas into your car at a Valero (NYSE:VLO) station? Are you in agriculture, with a great familiarity with and respect for Deere (NYSE:DE) products? Well, TD Ameritrade and Valero have seen their stock more than quadruple over the past decade. Deere has nearly tripled. These companies have performed rather well, right under our noses.

Beware what you don't
Along those same lines, be wary of what you don't understand. If you don't understand how a business makes money, you probably won't be able to tell when business is going badly. Biotechnology companies present a good example, as do new-technology companies. Think of Elan (NYSE:ELN) -- if you're invested in it, do you have a good grasp of its current and in-the-pipeline therapies for neurology, autoimmune diseases, and severe pain, among other things? How about the pipelines of its key competitors? If you're invested in Corning (NYSE:GLW), are you familiar with current and expected demand for specialty glass and ceramics? Do you have a good grasp of Corning's competitive advantages?

You don't have to invest in hard-to-understand companies to do well. Think of Caterpillar (NYSE:CAT), for example, which has increased in value more than eight-fold over the past 20 years, with a market-trouncing average annual growth rate of more than 11%.

Hang on for the ride
If you buy into a company hoping that it will be a multibagger for you, buy to hold as long as you continue to understand the business, strategy, and leadership. If you have faith in the company's future, it's often best to just hang on, despite inevitable hiccups. If you still have long-term confidence, don't let naysayers in the media get you out of a stock because of short-term concerns.

Consider Wal-Mart. For its earliest investors, it's been more than a 1,000-bagger over roughly 35 years. For those who've hung on for a little more than the past decade, during much of which the stock has been stalled, it has more than doubled their money.

Similarly, those who hung on to software specialist Quality Systems for the long haul after it was first recommended in our Motley Fool Stock Advisor newsletter some five years ago are now up more than 600%. (Those who sold after doubling their money have ... well ... only doubled their money.)

Sell if things get too crazy
Consider selling some of your shares if they hit levels you can't justify or if the company is facing some long-term problems. That was my main mistake -- irrationally and greedily hoping to get even richer. If a stock is trading for far more than you know it's worth, and you still hang on, you're no longer investing -- you're speculating, and at great risk.

This kind of issue is what investors in companies such as customer information management specialist need to think about. Its stock was recently trading at a P/E ratio above 100, based on trailing-12-month earnings. Is that reasonable, or has the stock gotten ahead of itself?

Get help from the pros
Finally, consider checking out the stocks that David and Tom Gardner recommend. (Or invest on your own -- this is, according to some, the best investing opportunity in 35 years.) Their Motley Fool Stock Advisor service, launched more than six years ago, offers two picks (and two investing styles) each month. They have a few losers, of course, but on average, their recommendations are beating the S&P 500 by more than 27 percentage points.

I invite you to try Stock Advisor free for 30 days, when you'll have full access to all past issues and recommendations. I've found some good stocks for my own portfolio there.

Here's to big profits in your future!   

This article was originally published Feb. 2, 2006. It has been updated.

Longtime contributor Selena Maranjian owns shares of Time Warner and Wal-Mart. Quality Systems is a Motley Fool Stock Advisor pick. Wal-Mart is an Inside Value recommendation. The Motley Fool is Fools writing for Fools.