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How do you short stocks, and what does a "short squeeze" mean? And when does a squeeze generally occur? Thanks, M.L.

Selling short is a way investors make money on stocks they believe are going to decline in price in the near future. The important rule to remember is that shorting, while offering a smart way to make bearish bets, carries significant downside risks.

To sell a stock short, you borrow the shares from your broker, then sell the shares and hold the money and wait for the stock to fall. If it does fall, you buy the shares at the lower price and give them back to your broker, who gets a commission and interest for his troubles.

For example, you borrow 100 shares of

IBM

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at $100 a share (a hypothetical price to make the calculation easier) from your broker, then sell them for $10,000.

Let's say the stock drops 20% to $80 a share; you buy the shares back for $8,000, then return them to your broker and pocket your $2,000 profit -- minus your broker's commission, which is the same as what you would pay on a stock purchase, and interest.

Now, let's examine the other side.

If you short a stock whose price rises, things can get hairy. You can wait to see if the stock will decline, or you buy the stock back at a higher price than you sold them and give them back to your broker (along with the other fees) and take the loss.

Those are the basics. Now let's go over the specifics regarding short sales and execution rules.

When you designate an order as a short sale, you are borrowing the shares from your broker. Your broker sets up a margin account -- it's a credit that has to be repaid at some time, depending on the discretion of your brokerage firm. An initial investment of $2,000 is mandatory to set up a margin account. You are required to deposit at least 50% of the stock price in the account.

If the stock you are shorting rises, the account is subject to a maintenance margin -- investors have to put more money into the account. The regulations governing margin accounts are a bit more stringent on short sales: For every 20% gain in the stock price, you have to funnel another 30% into the margin account.

While margin requirements vary at different brokerage firms, buying or shorting stocks on margin carries heavy risks for the average investor.

Don't Get Squeezed

Now we get to the squeeze part. When you close out a short sale, known as short-covering, you repurchase the shares and give them back to your broker. Covering your short position at a loss can get ugly during a short squeeze. A squeeze occurs when a stock that has been shorted by many investors rises. More and more short-sellers must buy shares to cover their short positions, putting greater upward pressure on the stock price.

You can short a stock for as long as you want, unless your broker demands you give back the stock that you borrowed, which doesn't happen often. When you return the shares to the broker, you have to pay any dividends the company hands out.

There also are some restrictions on short-selling that may discourage some investors from giving it a go. You can't short-sell stocks that are trading below $5. Also, the price at which you short a stock must be at the market price or higher -- thanks to the uptick rule, which was instituted to avert continuous short-selling during a market decline, as was witnessed in the 1929 crash. (Exchange-traded funds, or ETFs, however, are not subject to the uptick rule.)

Also a key note for individuals: Most short sales must be executed in round lots of 100 shares.

Because of the costs and risks associated with short-selling, most individuals have no real need for short-selling in a diversified portfolio.

However, many financial planners suggest that individuals satisfy their urge for betting on the market by making side bets -- with less than 5% of one's investments -- on individual stocks. As long as an investor is aware of the additional pitfalls and realizes the potential for limitless losses, short-selling can make for a reasonable side bet. The trick, as with standard stock investing, is picking the right stocks.

Unfortunately, even if you do an in-depth fundamental analysis of a company and determine the stock is overvalued, the share price can still climb because of market momentum, causing some serious damage.

Investors looking to protect their short bets should consider two simple measures. First, set a limit on how much you are willing to lose on a short bet, and stick to it. Second, investors should consider hedging their bets by buying call options, which increase in value when a stock goes up.