Sort groceries before you get home. At the market, ask the bagger to put all the perishables in one bag, the snacks in another, the canned goods in a third. You can help the process along by loading like foods together on the conveyor belt. At home, unloading will go far more quickly and be easier to delegate.
Prep meat and fish. The few minutes it takes to trim or pound meat can be sandwiched in between the flipping of the breakfast pancakes or afternoon calls to doctors and plumbers. Come suppertime, just pull your pan-ready fillets from the plastic bag and cook.
Meat can sit in an oil-based marinade for about 24 hours in the refrigerator, so you can set up the next day's dinner before hitting the sack; fish, with its more delicate flesh, should sit for no more than 4 to 6 hours, so this is something you might do at lunchtime. Place the meat or fish and the marinade in a resealable plastic bag, pop it into the refrigerator, and flip the bag once or twice during the day if you can; the food will be ready when you are. When you use a marinade made with an acid, such as lemon juice or vinegar, which actually begins cooking the food, pre-prep may or may not work for you, since meat should sit for less than 2 hours, fish for only 30 minutes or so.
Chop vegetables. "Onions, peppers, broccoli, zucchini, squash ― they can all be chopped ahead," says caterer Peter Callahan of Callahan Catering, in New York City. "Just cover them with a damp paper towel to keep the cut ends from drying out, then refrigerate." If you won't need the vegetables for up to 12 hours, pop them, towel and all, into a plastic bag. (Onions and other frequently used vegetables can be chopped, then frozen in plastic for 3 weeks.)
Vegetables and fruits that brown when cut can be stored in the refrigerator in a bowl of ice water with a squeeze of lemon ― "overnight for meaty vegetables, like potatoes and fennel; a few hours for soft fruits, like pears and apples," says Kurt Beadell, the creative director of the Portland, Oregon, restaurant-caterer Salvador Mollys.
Parboil vegetables. If you are using several vegetables for a stir-fry or will be serving them with a hot sauce, parboil them early in the day so you'll only be warming them up at dinner. Boil vegetables until they're almost tender, "shock" them in a bowl of ice water, drain, and refrigerate in plastic. You can do the same with vegetables you don't want quite raw on a crudité platter or in a salad, such as broccoli, carrots, and asparagus. The brief cooking preserves the bright colors, keeping the vegetables looking pretty. (For a complete primer on shocking vegetables, see The Secret to Perfectly Cooked Vegetables.)
Measure up. Holding a jangling set of measuring spoons over a boiling pot as you add spices isn't ideal (especially when the cayenne overflows and you get 3 teaspoons instead of one). Measure ahead of time, combining all the spices you need for a dish in a plastic bag or a small bowl. This gives you a head start and helps keep you from forgetting a spice or a garnish when you're rushing to put the meal together. "When you're ready to cook, you just dump, dump, dump," says chef Jennifer Bushman, author of Kitchen Coach: Family Meals (Wiley, $20, amazon.com).