1. Don't Prepare Garlic and Onions in Advance
Chopping garlic and onions releases sharp odors and strong flavors that become overpowering with time, so it's best to cut them at the last minute. Soaking sliced or chopped onions in a solution of baking soda and water (1 tablespoon per cup of water) tames their pungency for raw applications; just be sure to rinse them thoroughly before using.
2. Don't Seed Tomatoes
The seeds and surrounding "jelly" contain most of the flavor, so don't seed tomatoes unless called for in a recipe where excess moisture will ruin a dish.
3. Keep Fats Tasting Fresh
The fats in butter, oils, and nuts can go rancid and impart off-flavors to your cooking. Minimize their exposure to oxygen and light to slow down this process. Store butter and nuts in the freezer, keep nut oils in the fridge, and store vegetable oils in a dark pantry.
4. Strike Only When the Pan Is Hot
The temperature of the cooking surface will drop the minute food is added, so don't rush the preheating step at the start of most sautés. Wait for the oil to shimmer when cooking vegetables. When cooking proteins, wait until you see the first wisps of smoke rise from the oil.
5. Never Discard the Fond
Those caramelized browned bits that stick to the bottom of the pan after cooking are packed with savory flavor. Deglaze the hot pan with liquid (wine, broth, or juice) and scrape the bits free with a wooden spoon to incorporate the fond into sauces, soups, or stews.
6. Season with Sugar, Too
Browned food tastes better, and the best way to accelerate this process is with a pinch of sugar sprinkled on lean proteins (chicken and seafood) or vegetables.