Examine the frame of the sofa or chair by moving the piece around. Check for sturdiness and stability. See if it wiggles or shakes. The most important part of the upholstered piece goes unseen. The frame should be made of hardwood (maple, oak, ash, birch) and assembled using dowel joints with reinforced braces glued and screwed to the corners. Nails and staples are never used in fine furniture. Research the brand or company of the furniture you are considering to gain insight into construction techniques. A reputable furniture dealer can help.
Sit on it. Lie down on it. Decide if it's comfortable. Determine if there is enough depth in the seat or too much. Cushioning materials may be polyester batting, high density foam polyurethane, down and feathers or a combination of these materials. Shredded or rubberized fibers are found in lesser quality cushions. What supports the cushion is important. Eight-way hand-tied coil springs are still the industry standard. Sinuous wire springs are desirable as well. Sinuous springs are used in slim design pieces that cannot handle the bulk of coil springs.
Find out the fabric's grade. Each fabric is graded for durablility and cost; the higher the letter grade, the more enduring and expensive the fabric will be. Tightly woven fabrics are more durable than loosely woven ones. Both natural and synthetic fabrics can be excellent fabrics for their wear resistance.
Keep in mind the use for the furniture. A den sofa for a family with active children needs a better grade fabric than a parlor settee that will be used occassionally.
Inspect the finish of the case piece. Case pieces are unupholstered units such as chests of drawers, sideboards, china cabinets and bedside tables. The finish should be smooth with even coloring and a mellow patina that comes from lots of rubbing. The finish will be resistant to scratches and spills. The grain of the wood will shine through, according to Phyllis Allen and Miriam Stimpson of "Beginnings of Interior Environment."
Slide the drawers in and out. They should operate easily. Examine the construction of the drawers. They should have dovetailed fronts and backs, center drawer guides, dust panels between drawers and the drawer bottoms should be held by grooves.
Take notice of the case itself. The joinery should be mortise and tenon, dowel, miter, dovetail or tongue and groove. Fine furniture will not have butt joints. The legs or base support should be sturdy, and, generally, reinforced with blocks that are screwed and glued.