Chef Ron Viloria says there are three tools involved in telling when food is done: your senses, timing and temperature. Each has its uses and its drawbacks.

Oh, and there's a fourth, the patience to pay attention to the clues your tools are giving you.

Professionals often rely on sight, sound, smell and touch alone. "Cooks who have been working on the line for years, they will go by touch. They know their grill, where the hots spots are and the cooler spots. They know the cuts of meat they're working with," said Viloria, newly appointed executive chef of Tiki's Grill & Bar at the ResortQuest Waikiki Beach Hotel. But most home cooks lack the experience to rely only on their senses unless they're very, very familiar with a dish.

Timing — "roast 15 minutes per pound" — is a problem because many factors can affect the length of time needed to cook things properly, Viloria said. Among these: the temperature of the food when you begin cooking, whether a cut of meat is bone-in, whether it's uniformly shaped or a combination of thick and thin, whether the oven is properly calibrated. Before grilling or roasting, he suggested, bring meat or fish to room temperature to speed up cooking time. Every few months, check your oven's temperature with a thermometer to be sure it's accurate, especially if you do a lot of baking, where a matter of a few minutes at the wrong temperature can mean a failure. Bone-in meat and whole cuts require extra care to keep from overdoing the more delicate parts; this may require protecting some parts with foil.

Temperature is the most accurate predictor of doneness and is useful with all the trickiest dishes, Viloria said. Anybody can tell when a casserole is done and pies can be gauged by the color of the crust. But meat, fish, breads and other baked goods, custards and puddings can look beautifully done when they're still raw —or, conversely, when they're overdone and dried out. Check a chef's jacket pocket and you'll see clipped there a standard tool of the trade that is only now making it into home kitchen drawers: the instant-read thermometer. These thermometers have been available — and reasonably priced — for years, but many cooks still think they don't need one.

This type of thermometer has a sensor in the tip that quickly reads the temperature of whatever it's touching. They are not left in the food, like old-fashioned styles used in roasting turkeys or other meat, but plunged in when you want a reading. Viloria said some old-school chefs don't like to use thermometers on meat because they don't want to pierce the skin and allow juices to run out. But he thinks the trade-off is worth it to avoid a dry, rubbery steak — or an unsafe one.

Viloria doesn't use a thermometer for fish; he relies on his eyes, checking the edges for changes in color and pressing with his finger to see if the fish has firmed up. And, although they wouldn't do this in a restaurant (for appearance sake), at home it's perfectly OK to insert the tip of a knife in the center of the fish and gently open a small seam to check for doneness.