kathy2477 has written a very honest informative guide here and I would like to add a few words of advice of my own. For clarinettists this advice will go without saying but for parents buying instruments for...
Before we start, let me make one thing very, very clear: DO NOT, UNDER ANY CIRCUMSTANCES BUY THOSE DODGY CHINESE CLARINETS! They may be cheap, and look good, but trust me: they are the poorest quality...
As a woodwind musician hopefully some of this will help non-musical sellers out when listing instruments. There are some important details that buyers are interested in and it will save sellers a lot of time...