(MONEY Magazine) – For eight years Jack Keller, 44, made an enviable living as a professional poker player. All told, he earned $1.1 million and this year was ranked the second leading money winner in the World Series of Poker. Last July he quit to become a trader at the Chicago Board Options Exchange. Ask him why he gave up gilded casinos for gladiatorial trading pits and he will tell you he felt burnt out, that he did not want his two sons, Jack Jr., 13, and Scott, 11, to take up their dad's livelihood, and that he yearned for more time to spend with his wife of 20 years, Gloria, in their new home in suburban Winnetka. Keller's current partner, Jerry Krause, spotted him competing against 350 others at a Las Vegas poker tournament in May 1986. Krause lured him to Chicago with an unlimited guarantee against trading losses and staked him to $50,000. At the CBOE, Keller is one of about 15 marketmakers -- traders who buy and sell options for their own accounts rather than act as brokers for the public -- in Polaroid stock. A call option is a contract that gives the buyer the right, but not the obligation, to purchase 100 shares of a stock from the option seller at a preset price -- known as the strike price -- within a specified period, usually nine months or less. A put is the reverse -- an option to sell. A call goes up in price when a stock rises; a put, when a stock falls. As a marketmaker with minimal commission costs, Keller is able to trade huge numbers of options, profiting from small price fluctuations. He uses computer-based models that identify options selling below their inherent value. His gut instincts for figuring the odds, weighing risk and acting decisively are as much the hallmarks of a successful trader as they are of a steely poker champ. ''The difference,'' says Keller, ''is that trading can be much more lucrative.'' Individual investors cannot hope to attempt the sophisticated -- and risky -- strategies that a marketmaker employs. But Keller offers these five rules for those who want to speculate with options: Deal with a knowledgeable broker. One who is experienced in options and has access to a computerized model can identify bargain puts and calls. You are most likely to come out ahead if you consistently buy undervalued calls. Know your stock. Options have value when they expire only if the underlying stock has moved past the option's strike price. For example, an option to buy a stock at $40 will be worthless if the stock is trading at $39 at expiration. With the stock at $42, the option will be worth $2 ($42 minus $40). You should therefore check the volatility and price history of the stock to be sure that it has a reasonable chance of moving far enough in a short space of time to make your option worth more than what you paid for it. Do not risk all your money on one option. No matter how cheap it looks or how enthusiastic you are about the underlying stock, you should never put more than 10% of your risk capital into a single trade. Think ahead. Decide in advance what you will do if a trade is not working out. If a stock does not move, the mere passage of time will erode the price of an option. And, of course, if the stock goes in the wrong direction, the option's value will melt away even faster. Have a target sell price and stick to it. Set realistic profit goals. If you do not believe you have a good chance of making 50% on an option, skip it. Consider selling your option as soon as it doubles in price. At the very least, sell half of your option contracts once the price has doubled. That way, you will recover your investment and let your profits ride.