How can consumers be more responsible and make food shopping more pleasurable? Food-industry expert Phil Lempert offers some tips:* Make a list. Stick to it with a five-item-over limit. Ask yourself: "Do I really need it?" * Read labels. "More and more people are reading labels, but that doesn't mean they're understanding them," says Mr. Lempert. * Be skeptical. "You can't be lazy. You can't rely just on what you think a product is by the labeling or advertising." * Compare prices. If you're happy with a product, stick with it. But you can still be open to other products. * Keep the environment in mind. Ask yourself: How is the product packaged? Many times more packaging means more money and also wasted money. Plastic vs. paper bag? Lempert says the life cycles of each are about the same, environmentally speaking. Best option: Bring your own. Be sure to wash your canvas and mesh bags. * If you're not happy, complain. Talk with the supermarket manager, or if it's a product, call the 800 number. Or write Phil Lempert: Consumer Insight, P.O. Box 585, Montclair, N.J. 07042. Conversely, if a great product comes out it might worthwhile to call the 800 number as well.