For prospective antique furniture buyers, here's a quick primer to help in your quest:
You don't have to be an expert in Xylology (the study of wood), to identify a fake or reproduction, but a basic knowledge of wood and its history in furniture making is helpful. Oak is probably the most common wood you'll find in your furniture quest. Oak is a popular hardwood component in many older and newer pieces, and the preferential wood used in European furniture prior to the 1700's. At the turn of the 1900's, oak found renewed popularity in American furniture manufacturing.
Also popular into the first quarter of the 18th century, both in Europe and the colonies, was walnut. Cupboards, chairs and chests were frequently made from this wood. By the mid-1700's, mahogany surged ahead as a wood of choice due to its beauty and durability. Mahogany was ideal for making fine furniture pieces such as Chippendale dining sets.
In the 1800's, maple was used more sparingly, but was just as coveted. Birds-eye or tiger grains added considerable style to furniture pieces and makers would often use maple veneers to cover other lesser quality woods.
If plywood or particle board is found anywhere in an "antique" furniture item, it is a clear indication that it's a newer piece.
Older furniture can sometimes be dated by styles of dovetail joints or types of nails used. Dovetails are the interlocking "fingers" that connect two pieces of wood, as evident on the sides of drawers. They were hand cut to help strengthen the joint. Two, three, or four finger dovetails were used up to the late 1800's, and larger dovetails usually signified simpler country-made furniture. In the 1870's, American furniture makers replaced the traditional dovetail with a "pin and cove" style (basically a round dovetail) that can be seen on Eastlake or Victorian furniture. As aesthetically pleasing as it was, this style never found popularity outside the U.S.
After the 1890's, furniture was being mass produced, and factory machinery was able to replicate the hand cut dovetails with five or more fingers. English cabinetmakers were the exception however. They continued to hand cut dovetails well into the late 1930's, but by the 1950's, the entire industry switched to machine manufacturing. Today, nails and staples have replaced the dovetail, and only specialty shops that replicate antique furniture uses the centuries old dovetail process.
Nails are another easy age identifier. Antique furniture nails, particularly before 1790, were hand forged and had a rose shaped head. Subsequent to 1790, the nails were machine cut and the heads were forged by a blacksmith into a square shape. From 1830 to 1890, nails were machine cut and had a rectangular appearance. After the 1890's, nails were manufactured as we know the modern nail of today. Contrary to popular belief, furniture makers of the 19th century did use screws. These were hand forged after the 1830's and can be identified by their irregular appearance.
When determining age, do an overall inspection. Most furniture work was done by hand tools and will show "imperfections". Undulating surfaces of drawer undersides or backboards will indicate a hand planer (prior to 1850's). Circular saw marks will indicate furniture likely made after the 1830's.
Wood will shrink with age and the finish will darken. Joints, panels and inserts in antiques will be irregular or loose fitting and can indicate a genuine older piece. Wood shrinks against the grain, and consequently, an antique round table will measure slightly oval (longer at direction of the grain).
The original finish of an antique will have a naturally darker patina, as opposed to an artificially distressed finish. Shellac was a commonly used finish prior to the mid 1800's. Lacquer and varnish were developed after the 1860's. If your piece has either of those two later finishes, it is a clear indicator that it is a newer piece.
When identifying antique furniture, a magnifying glass or loop is a useful tool, as well as common sense. You should look for imperfections and non-uniform hardware or construction. With antique furniture, if it's too perfect, it may not be the real thing.