I have just completed my first full year of having a comment book FORMALLY
available for each and every exhibition, with a sign above it welcoming
comments (and proposing some questions to answer).

I have found that if I suggested some topics to write about (for example,
for a recent exhibition of artists chosen by local critics with criticism
posted next to the artwork I asked people to write about whether they read
criticism and if they thought it was OK to disagree with critics) I got
better comments that if I just put out the book and called visitors'
attention to it.  Visitors didn't always write about the suggested topics,
either.

I think anytime you ask for feedback you a) ensure people will look at the
exhibit if only to have something coherent to say, and b) empower people to
even feel comfortable having opinions.

Julia Moore
Indianapolis Art Center