WHEN Linda Lipsky taught a course called ''So You Want to Open a Restaurant'' at Temple University in Philadelphia, she deliberately made the business sound like a minefield. She warned her students that it is possible to lose their homes, their life savings, and even the rights to their own names. Her goal, she said, was ''to get two-thirds of them to quit.'' In fact, two of every three new restaurants, delis and food shops close within three years of opening, according to federal government statistics, the same failure rate for small businesses in general. ''It's very easy to fail if you know what you're doing, and even easier if you don't,'' said Ms. Lipsky, president of Linda Lipsky Restaurant Consultants, a firm based outside Philadelphia that has advised restaurant owners and chains for 20 years. [ABSTRACT FROM PUBLISHER]