July is National Grilling Month. To celebrate, "Low & Slow" co-author Colleen Rush will be offering up vital bits of barbecue wisdom every Thursday throughout the month.

Whether you're using gas or charcoal (we prefer charcoal), there are two ways to cook with fire -- either the meat is cooked on the grate right over the flames (aka "direct heat"), or it's set on a cooler part of the grate, away from the flames ("indirect heat"). How, when and why you use these two forms of heat depends on the meat and the cooker.

After the jump, get a rundown of the finer points of using direct and indirect heat when barbecuing.


DIRECT HEAT
Cooking food directly over hot coals or a gas flame is "grilling" -- it cooks hot and fast. The intense heat (approximately 400-500 degrees Fahrenheit, or hotter) and flame quickly sears the surface of meat, which produces a crusty, caramelized exterior without overcooking the interior of the meat. Typically, after the meat is seared, you want to move it to an indirect heat zone to finish cooking and keep the exterior from getting charred. Direct grilling is the method to use on smaller cuts of meat that cook quickly (think: hot dogs, burgers, sausages, chicken breasts) or meats you want to sear on the outside but keep the inside rare or medium-rare, like thick Porterhouse steaks or a piece of Ahi tuna.

The Setup
Simply fire up your cooker the way you probably always do -- with a big batch of charcoal spread evenly across the charcoal grate, or all burners cranked up on your gas grill. If you're cooking on a charcoal grill, open all vents, top and bottom, to ensure good airflow. Air blowing over the coals keeps them burning red-hot.

Wait until the cooker is very hot before you throw on the meat. The built-in thermometers on grills are notoriously inaccurate -- off by as much as 200 degrees. Do not rely on your cooker's thermometer. To check the heat, hold your hand about 4 inches over the hot grate. If it's too hot to keep your hand over the grate for more than three seconds, it's hot enough to start grilling.

INDIRECT HEAT
This is "low and slow" cookery, or what traditionalists refer to as barbecue: cooking at a lower temperature (anywhere from 225-275 degrees) away from the direct charcoal or gas flame. The lid of the cooker stays closed to hold in the hot, circulating air and smoke, which cooks the meat by convection. This slow-cook method is ideal for turning big, tough, fatty cuts of meat, like pork shoulder, spare ribs or baby back ribs, into rich, tender barbecue.

The Setup
Bank a pile of lit charcoal on one side of the charcoal grate. For best results, place an aluminum loaf pan filled with water (about 1 inch below the edge to keep it from boiling over into the fire) on the cooking grate over the pile of charcoal. This water pan acts as a heat stabilizer in the cooker -- moderating the heat of the fire, and protecting meat on the grate from the direct blast of the fire's heat. Place the meat on the cooking grate, opposite the water pan and banked pile of charcoal. Close the bottom vent(s) by about a third, but keep the top vent completely open to ensure proper airflow.

For an indirect cook on a gas grill, light one back or side burner (depending on the layout of the burners). Place the meat at the far end of the cooking grate over the unlit burners.

To keep an eye on the grate temperature in the cooker, set a cheap oven thermometer on the grate next to the meat, away from the fire.

Grilling Guidance Week #1 -- Marinades and Brines
Grilling Guidance Week #2 -- Charcoal Versus Gas