What am I looking for?
The fingerboard should be smooth; the strings should clear the fingerboard along the entire length. The nut should just allow a business card to be inserted under the strings next to the nut. Vibrating strings eventually wear down the fingerboard and nut, causing grooves that can be quite deep. This is a common cause of buzzes and other unpleasant sounds. The fingerboard will have to be ‘dressed’ or re-planed; the nut reshaped or replaced. This is a job for your luthier.