the American Quilters Society has a 'course' and trains appraisers. if you take your quilt to a Certified Quilt Appraiser you will receive a written report on your quilt and the (Insurance value). it is well worth the $$ to have special quilts appraised. if the appraisal is done at a show often the appraiser will look carefully at the quilt, take measurements, ect then also will take a number of pictures. then they (go home) you recieve your written appraisal in the mail a couple weeks later.
i would always make sure the person who is doing the appraisal is a CERTIFIED APPRAISER - if the person is not- your appraisal may not mean much if you need an insurance claim or are giving the quilt away.