You might find: reupholstery and recaning. The frame is the important part. Fabric and cane will understandably deteriorate over time. But the wood -- the skeletal bones of the piece -- is of primary importance.
Steer clear of: replaced legs and/or feet, alterations of height, and wood that has been refinished. Feet were often damaged due to cleaning and wear, so look underneath the piece for different wear patterns on one or more feet. Look at the overall proportions; sometimes banded cuffs of inlay can hide the addition of height. Keep in mind that carved or splayed legs can be especially vulnerable to breaks.
