Well, everybody knows seasoned wood is the best. But do we all know what "seasoned wood" means? In short it basically means wood that has been air dried so it contains only a 15%-20% moisture content.
So, why is seasoned wood better for burning?
It gives off less smoke for one thing, plus it burns hotter and more efficiently, reducing your wood consumption by up to 25%. Because of these reasons it is preferable to green wood for burning. It also weighs less than green wood.
To season your own wood, Bob Vila (Seasoned Wood) recommends giving it a home in a spot that is open and dry, and if possible hit by the sun, for about six months. Another site, The Healthy Wood Stove Campaign, further suggests you split your firewood and stack it in a criss-cross pattern on a platform to ensure even drying all around.