“Well Seasoned” wood will typically have been left to dry in a sunny, well-aired space for one or two summers and kept dry over the winter in a log store. Radial cracks and bark that comes off easily suggest well-seasoned wood; better still, check with a moisture meter. Do not burn treated waste wood (e.g. old furniture) as it can emit harmful fumes. Burning good quality wood is very important – kiln dried wood, particularly ash, beech and birch, burns particularly well but whatever the species used, the moisture levels should be no more than 24%.
