To use wood for smoking, soak it for thirty minutes to one hour in water to cover. This slows the rate of combustion so the wood smolders and smokes. Toss the wood on lit charcoal, which will provide the actual heat (that’s why it’s so easy to smoke on a charcoal grill).
Almost any hardwood is a candidate for grilling (hardwood comes from deciduous trees—trees that lose their leaves in winter). The short list of commonly used woods for smoking includes oak, hickory, maple, alder, and fruitwoods, like apple, pear, and cherry. Never use a softwood like pine or spruce; the smoke will be unpleasant and oily tasting. Some softwood smoke is actually toxic. And never smoke with plywood or pressure-treated lumber, which contain toxic chemicals.