Charcoal alone will add a mild, smokey flavor to grilled foods, and for some dishes — fruits, vegetables, and mild, white fish — that's enough.
But getting a good, red, smokey SMELL into a large, tough roast of beef or pork requires a few extra accoutrements. At the top of this list are two things: chips and chunks.
Almost all commercially packaged wood chips and chunks are made from hardwood trees - and the most common choices are hickory, mesquite, alder (north of the Mason Dixon), and occasionally cherry or oak. Our reservation about the term "hardwoods' comes from smoking foods on cedar planks, which isn't a hardwood, but it's not resin-filled yellow southern pine, either. Never use pine in your pit - it gives off resinous fumes that will eventually give the inside of your grill a nasty, turpentine-based smell, and there's nothing tasty about that. If you decide to go the DIY route with the wood chips, stick to well-known species such as hickory, pecan, and fruit woods for the best flavors and smells.
The real difference between chips and chunks - the obvious size, of course — results in the chips lasting on the coals for about 20-30 mins, while the chunks can puff along for over an hour without replacing. While this might be a small matter when grilling flatbreads or smoked trout - every barbecue grillmaster worth his salt will tell you that he NEVER EVER opens his pit willingly. Adding coals and chips to the fire is one of his most precarious tasks, resulting in a precipitous drop in pit temperature — a temperature monitored more closely and lovingly than the tenderest newborn babe. No kidding - it can take up to 30-40 mins to get the pit back up to the correct temp (usually around 250 degrees) after a long opening to re-stock the fire. Time lost = Temp lost = Tender lost.
Now, we're not usually that competitive, and our smaller, family-size grills re-heat quickly. We still believe that if something's a real pain to do, you won't do it at all — or you won't do it as often — so make the chore of tending the grill as easy as you can.
If you're looking for a light, smokey taste on a quick-cooking dish, use the chips, and soak them for at least 30 mins in some wonderful liquid, like apple juice or beer. Avoid any liquid with a higher alcohol content than beer — or oil — or your chips will go up in flames. If you are braising long-cooking cuts like pork butt or beef brisket, use the chunks. Soak them overnight if you can and use several of them, placed right down in the coal bed. If your brisket is cooking for 10 hours, you will have to replace the chunks when you add more coals to the grill — probably hourly.
If you use a gas grill, you will only use the chips, since you don't have a coal bed to nestle the chunks down on, but that's OK. The chips will still help you get a smokey flavor that you won't get any other way. Wrap the wet chips a couple of times around with aluminium foil and seal up the ends of the packet. Make some large holes in the top of the packet and nestle the whole thing down in the bottom of the grill by the burners. Start the chips before you start the food, so they have time to get smoking!
