Two authors with extensive retail experience selling European and American furniture have written a booklet, ''Things They Might Not Tell You at the Furniture Store'' (Straight Facts Publishing, Damascus, Md.), in which they tell all.
Well, not all. The authors, who wish to remain anonymous, don't give manufacturers' or retailers' names, but they do point out shoddy practices they've seen and include questions buyers should ask.
The quality of craftsmanship, they say, is improving. ''There's a swing toward trying to build a better piece of furniture in America,'' one author said in a telephone interview. ''Some manufacturers are out there to stay in business for centuries.''
Those that are should appreciate customers who thoroughly check out their wares, using the following guidelines.
Upholstered furniture. Here's a one-minute test to run on a new sofa:
* Shake the arms - there should be no movement.
* Check for padding in the outer and inner arm, which increases both comfort and the fabric life.
* Check for a metal spring system in the seat and the back.
* Check for reversible cushions; they are longer lasting than one-sided cushions.
* Lift the front edge of the sofa about six inches off the floor to see if the whole piece goes up in a straight line as it should or sags in the middle.
The authors point out that most of the quality in an upholstered piece is hidden, so they advise asking for specifications (most good-quality manufacturers have brochures) and making sure the piece holds a UFAC (Upholstered Furniture Action Council) tag. They also suggest that only hardwoods be used in construction (at least 11/2 inches thick) for extra strength. The customer should ask if bolsters and arm covers come with the piece (''what you see isn't necessarily what you get'').
They warn customers about measurements on sleep sofas, saying the length of most of these is 70 to 72 inches, whereas the standard full-size mattress is 75 inches long - something to think about when you're buying sheets. Another problem piece is the sleep sofa that folds the mattress three times - the mattress is longer, but it's also thinner and less comfortable.
Wooden chairs. The authors have seen repeated problems with wooden folding chairs, which they say are often braced with only a 1/4-inch piece of wood. Twist in the seat when trying it out, they say. And be sure to take your coat off in the winter before trying any chair; some retailers put out their most uncomfortable items when they know customers will be wearing extra padding.
The authors also have a couple of quick tests for rocking chairs. First, listen for any noises while rocking - noises that, in their experience, will not disappear with time. Then sit all the way back in the rocker and extend your legs straight out. If you find you are tipping forward, look for another chair.
Bureaus and buffets. Most United States manufacturers, the authors point out, use center-glide support systems for drawers, which work best when the drawer slides along two plastic or nylon glides under each edge of the drawer. European-made drawers are side hung, and the cheaper models may slip off the tracks. In good-quality side-hung drawers, there should be only 1/8 to 3/16 inch of ''play'' between the drawer and the bureau. Try moving the drawer from side to side.
The chief feature to look at on buffets is the legs. The authors think the best models have none, but are built with a box base. They warn customers to beware of those with legs on the outer edges or sides extended to make legs - buffets four feet or longer between the legs will sag with heavy use.
Mattresses. The authors say these are ''nearly impossible'' to compare, but there are a few signs of quality. First, make sure the mattress has at least a one-year warranty, ''and try to keep the bedding as clean as possible during the warranty period. Most bedding manufacturers will not repair or replace soiled bedding.''
If you're buying urethane foam mattresses, look for one with a weight of about three pounds per cubic foot, so fitted sheets don't make the edges curl up. For a firm mattress, the authors say, ''select one whose density/compression ratio is 30 pounds or more.''
Since about ''one-third of your life for the next decade or so will be spent on that mattress,'' the authors suggest that a couple try this test in the store: ''Both of you should roll together toward the middle of the mattress. Now each of you roll separately to the edge. Does the mattress still support you?''
Children's furniture. The ''biggest mistake most often made in buying children's furniture is that drawers and doors are not examined closely enough, '' the authors write. They advise that you let your child try opening them.
They also think factories sometimes cut costs on bunk beds by making them so they won't unstack or accommodate standard twin-size mattresses. The mattress of choice for a child's bed, the authors say, is foam, since ''innerspring mattresses can be damaged from children jumping on them.''