You need to identify your furniture by style and manufacturer before you can understand what a fair price is. Consult some books on older furniture in order to learn more about what you have. Here are some suggestions:
"Popular Furniture of the 1920s and 1930s" by Schiffer Books for Collectors is a reproduction of an old furniture catalog
"Furniture of the Depression Era" by Robert and Harriet Swedberg is out of print but can be found used online
"The Furniture Bible: Everything You Need to Know...." by Christophe Pourny
"The Encyclopedia of Furniture" by Joseph Aronson
"Furniture World Styles From Classic to Contemporary" by Judith Miller
Check the back and undersides of the furniture for labels.
Once you know what you have, comparison shop online (look at sold prices) or at local dealers to get some idea of the value.