There is no one correct answer to this question. As a rule, differences in woods and their uses determine the moisture content desired. For instance, if the wood is to be used in construction as a stud for building, the moisture content requirement could be 15% to 19%. If the wood is to be glued, and it is too dry it will not bond. If it is too wet, it will not hold. Ideally, the moisture content of wood to be used in furniture is between 6 and 8%.
The best way to determine the proper moisture content of the wood you are using is to contact the nearest university forest products department or trade organization for the wood product you are dealing with. You may also call the United States Department of Agriculture (USDA) Forest Products Research Laboratory in Madison, WI (608-231-9200).