Cooking on wood is not difficult, but it does take some common sense and a lot of patience. Here are some key things to keep in mind when choosing a wood.
The most important thing to remember, is not to cook on wood that has a high sap content like pine, spruce or cedar-evergreens. These kinds of wood also contain high levels of tannin, which is used primarily in curing animal hides. Cooking with these woods leave soot on the food and also can create hazardous smoke. Oak and maple also contain significant levels of sap and tannin, but when seasoned for 6 to 12 months they can generally be used with great results.
Hands down, the most desirable woods are fruit and nut tree woods. Hickory, pecan, cherry and apple work burn clean, produce an incredible flavor and can be used for smoking and grilling. One thing to remember is that fruit woods burn quickly, so blending with another hardwood like oak will create a nice flavor and prevent you from having to add wood or stoke the fire quite as often.