Measure the floor area where you want to lay the rug. Be aware of how much foot traffic and sunlight that the area receives. If you are buying a rug for hanging on the wall, plan to hang it out of direct sun and away from any place that's damp or cold.
Consult a dealer who imports from Iran, India and Turkey, where highly prized rugs are made. Talk to the dealer about patterns made in various regions of the Middle and Far East. Particularly sought-after are rugs made from the 16th to the 19th centuries. Oriental rugs made during the reign of Great Britain's Queen Victoria are more readily available, because production at that time rose to meet increased demand in the West.
Examine the wear and tear of the rug, noting unexplained and uniform areas of fading, dryness, brittleness and any damage or tears. Also look for any signs of a seam, which suggest that two rugs have been joined together. Less scrupulous dealers have been known to enhance colors by painting over faded sections and to age substandard rugs to pass them off as valuable antiques.
Look closely at the weave. Genuine handmade rugs are knotted, with specific geographic areas being known for their number of knots per square inch. Tufting, where wool is pushed into the warp and weft and then sealed on the back with an adhesive, is a mark of rugs of lesser quality. As the adhesive dries out and disintegrates, the wool tufts come loose.
Check the defining lines within the design. Manufactured rugs are consistent in pattern. Genuine hand-knotted rugs have mistakes in the pattern, and these are actually prized, as they are a mark of handmade work. Handmade rugs are usually full of anomalies, often with graphic signatures incorporated in the design as the weaver's mark.
Ask for a color fastness test. Genuine handmade rugs are made with vegetable-dyed wool, and the wool retains its lanolin. If you bend the rug just slightly to look at the wool, natural dyes will not take in all the filaments, whereas manufactured and chemically treated wool will be a uniform color throughout.
Ask to have the rug in your home for a week or two. A reputable dealer understands that a quality rug is bought as an investment and as a thing of beauty to be displayed for decades. It is important for you to see if the rug fits you and your home.