Wall Street is a tremendous pressure-cooker, with billions of dollars changing hands every single day. Most of that money is managed by institutions -- organizations that invest other people's money. Largely because of that, Wall Street runs by a set of unwritten rules that differ from the ones we individual investors follow. If you know these rules, you can exploit their weaknesses for your personal advantage -- and end up ahead.

Better yet, the way these unwritten rules work in practice, the less time you spend trying to beat the market, the better your chances become. Of course, market-beating investing is not an entirely passive business. You will have to tend your portfolio like a gardener. There will often be weeds to pull and excessive growth to cut back. In general, though, planting the right seeds and simply letting nature take its course is the best way to long-term success.

Unwritten rule No. 1: The short term is all that matters
Institutional investors' biggest problem is that they're managing other people's money. Ultimately, those other people control the purse strings, and they can yank their cash out if the institution fails to live up to their expectations. As a result, Wall Street institutions live and die by their relative performance against their respective indices and peers.

The reason is simple. If a mutual fund falls behind those benchmarks, money starts to flow out of the fund. If too much money cashes out, the fund could be forced to sell its positions, often at inopportune times. Selling stock at the wrong time often worsens underperformance, which leads to even more investor redemptions. It's a vicious cycle, and it's one of the primary reasons why so many gigantic funds like Fidelity Blue Chip Growth (FUND:FBGRX) have managed to trail the market over the long haul.

Because of their excessive focus on short-term results, these institutions tend to panic-sell whenever the news is even remotely bad. Take retailers Urban Outfitters' (NASDAQ:URBN) and Chico's (NYSE:CHS) recent woes. Despite being leading players in their profitable markets, they have been given 55% and 53% haircuts, respectively, from their 52-week highs. Why? Single digit same-store-sales figures (instead of the double digits investors were used to) and increased inventories sent Wall Street running for the hills.

This result added sufficient near-term uncertainty to the product's prospects, despite its still-legitimate potential for long-term success. Yet in typical Wall Street fashion, a setback that affects next quarter's numbers matters more than preparing to compete and survive 10 years from now. As such, Urban Outfitters and Chico's stock got hammered -- and hard.

How you can exploit it
Because the institutions focus so heavily on the short term, any weakness in a company's results or outlook triggers an exodus from its shares. Fortunately for you, that round of selling gives you the opportunity to absolutely crush the market. When a stock drops quickly, there's a very good chance that it will fall below its true worth. As an individual investor not bound by the short-term time frame, you can then buy it on sale. From that point, you simply wait for the panic to subside; when the stock returns to its fair value, you'll gain some extra returns for your patience.

This is precisely the strategy we employ at Motley Fool Inside Value, and it's exactly why lead analyst Philip Durell's picks have outperformed the S&P 500 index over the life of the service. We even have an online cash flow calculator available here (for subscribers only -- if you're not yet on board, click here to start a 30-day free trial) that will help you calculate a company's true value.

It's also why the Inside Value portfolio contains companies such as conglomerate titan 3M. Rivals Danaher (NYSE:DHR) and Dover (NYSE:DOV) have been outpacing 3M on a few key metrics in recent months, driving fear into the hearts of 3M's Wall Street investors. Yet these firms have a history of learning from each other's successes and failures over time. If and when 3M regains its footing, the panic sale should end, rewarding investors who held through the rough patch.

Unwritten rule No. 2: Too much of a good thing is bad
While underperforming its index and its peers causes too much money to leave a fund, doing too well can cause the opposite problem. Believe it or not, in the mutual fund world, there is such a thing as having too much money. Remember all the money pulled out of the funds that underperformed? For the most part, it gets immediately reinvested -- in the funds that recently outperformed their benchmarks or peers.

So why is this bad? For the most part, cash handed to a mutual fund must be invested. After all, would you pay someone 1% of your money every year to have it sit in a savings account at your local bank? Of course not! These same funds that panic-sell on bad news are forced to buy even more stocks if they're doing well. And which companies do they buy? Ones that have done well, of course -- stocks they already own that have strong recent price-performance numbers.

Your edge
Just as panic-selling can cause a stock to drop below its true value, too much buying can cause it to rise far above that worth. By using the Inside Value calculator, you can not only tell when a company may be underpriced and worth buying, but you can also tell when it's likely overpriced and in need of being pruned.

You probably would not have been able to sell telecom Qwest Communications (NYSE:Q) precisely at its bubble peak. You could, however, have used such a calculator to notice that its shares had reached uncomfortably lofty prices compared to their intrinsic value.

With a clear understanding of that fair value, you could have comfortably sold during its several-month run-up before the crash. There was no need to hurry, and no need to spend every waking minute watching the market. In fact, by spending less time following the stock, it would have been far easier for you to take that objective stance and determine that it was time to sell.

The Foolish bottom line
It's quite possible to beat Wall Street if you understand its unwritten rules and learn to exploit their weaknesses. Best of all, because those rules focus on short-term price moves rather than long-run value, you need not be a market junkie. Instead, you can crush the market in your spare time -- with long-term thinking and the power of value.

Do you like the idea of investing to beat the market without spending every minute of every day following stock movements? Subscribe to Inside Value today to start your journey.

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

Fool contributor and Inside Value team memberChuckSalettadoes not own shares of any company mentioned. 3M is an Inside Value recommendation. The Fool has adisclosure policy.