Knowing wood is the key to good firewood. Learn what trees in your area are good and plentiful. Oaks and maples grow in most regions and make good firewood. Many locales have ash, birch, beech, walnut and some fruit woods like pecan or cherry. Pines, cedars and other conifers grow in most regions but are not good firewood. Check with a local forestry office or university extension service for information on trees and how to identify them.
Checking weight is one way to help identify cut firewood. All stored firewood tends to weather to a sort of uniform grey, but weight will vary. Hardwoods like oak, ash and walnut will weigh about twice as much as softwoods like pine and cedar. Heft two logs -- the heavier one is probably a hardwood. This test can be deceptive for quality, however, hickory and elm varieties may weigh as much as oak or ash, but are not good firewood because they are very hard to split.
Another test is leaves and bark. Even cut firewood may have some twigs or branches with leaf remnants, which will help identify the tree. Get a leaf guide if you are not adept at identifying trees. Most cut logs also will have some bark, which can be a good identifier. Pines and cedars have easily recognisable rough bark, oaks and other hardwoods tend to have smoother bark. If you are uncertain, take bark to a forestry or extension office for help.
Grain will identify most firewood. Oaks, ashes, maples and others generally have straight fine grains running the length of the log. Pines, cedars and other softwoods usually have less visible grain than woods like elm and hickory, which have grains that twist and turn, which is why they are to hard to split. Try pulling some splinters off a log. Hardwoods should separate fairly easily.
Try splitting a log with a hatchet. If it splits easily and evenly, it's probably oak, walnut or a similar hardwood. This can be deceptive -- pine also usually splits easily, but its split edges will look different from those of good hardwoods and may actually be more even than oak. Smell the newly-split log. Oak and walnut, for instance, have easily recognisable odours. Pines and cedars tend to have pungent and easily identifiable smells. Try burning a small chunk; hardwoods will burn down to solid coals, softwoods usually to a pile of ashes.
The best way to identify cut firewood is to label it before stacking it into piles. Either write "oak" with a marker on the end of a log or make a diagram of your wood pile showing what wood is where.