Wood smoke is an integral part of the true barbecue. Wood comes in three forms for smoking: chips, chunks, and logs. Chips and chunks will handle the needs of most backyard grillers; logs are used by people with professional rigs and large front-loading charcoal grills.
For a light wood flavor, simply toss the chips or chunks on the coals-a technique used mainly in direct grilling in the style of Europe or South America. For a more pronounced smoke flavor-the sort associated with traditional American barbecue-soak the chips or chunks in water (or a mixture of water and beer) for 1 hour, then drain before adding them to the fire. This soaking causes the wood to smolder rather than burst into flames, so it generates more smoke.
By varying the wood, you can subtly vary the flavor: heavy woods, like mesquite and pecan, have a stronger smoke flavor than fruit woods, like apple or cherry. The best all purpose woods for smoking are hickory and oak. However, the difference is very subtle. Almost any hardwood can be used to for smoking with sublime results.
Note: NEVER attempt to smoke with softwoods or pressure treated lumber.
Smoking on a charcoal grill
To smoke on a charcoal grill, set up your grill for indirect grilling and toss the wood chips or chunks on the piles of glowing embers.
To smoke on a gas grill, check first to see if your grill has a smoker box (a long, slender drawer or box into which you can put wood chips for smoking). If it does, fill it with wood chips and light the burner under or next to it on high until you see smoke, then lower the heat of the grill to the desired temperature.
The smoker box on your gas grill
If your gas grill lacks a smoker box, make a smoker pouch: wrap the soaked chips in heavy duty foil to make a pillow shaped pouch. Poke a few holes in the top with a pencil or knife tip, and place the pouch under the grate over one of the burners. Preheat on high until you see smoke. Note: the traditional drawback to gas grills is that many don't get hot enough for smoking. Preheat the grill to high until you see smoke-lots of it-then turn the burner knobs to reduce the heat to the desired temperature.
Alternatively, position wood chunks under the grill grate directly over one of the burners or pilot lights and preheat on high until you see smoke.