What types of wood work best for smoke flavoring?

Wood chunks or sticks 3 to 4 inches long and 2 to 1 inch thick work best for smoke flavoring, using varieties such as hickory, pecan, apple, cherry, or mesquite. Unless the wood is still green, soak it in water for 20 minutes or wrap each piece in foil with several small holes torn in it to produce more smoke and prevent the wood from burning too quickly. A recommended starting amount is 3-4 wood chunks or sticks. (Page 2)