Combine a thickening agent like flour or starch with cold liquid before adding it to a sauce. The sauce will be less likely to have lumps. If lumps do form, beat them smooth with a wire whisk or purée the sauce in a blender.

When any sauce is "reduced," the water evaporates and concentrates the flavor of the sauce. That's why it's a good idea to increase the sauce for a recipe, if desired, but never omit this "reduction" step. For cream sauces, the butter fat content of heavy cream also thickens the sauce as it reduces.

If you use part of a jar of spaghetti sauce in a recipe, write the date you opened it on the label and use the rest promptly or freeze it.

Oyster sauce is a staple seasoning in Asian cuisine. It's a deep brown sauce made with oysters, brine and soy sauce. While it's extremely flavorful it doesn't overpower other flavors. Try it as a condiment, too.

Soy sauce is an extremely important ingredient in Asian cuisine. Dark and salty, it's made of fermented soy beans. You can find it in low sodium and light versions, too.