What are galleries looking for?

This one is almost an addendum to our December 8th episode ("You don't need a gallery for your solo show"), but every artist have a unique path and body of work, so here we go!A mid-career artist have a simple question about exhibiting his works: what are galleries looking for? What can he do to have more of his works accepted? But he knows the answer and maybe the question should be: what else besides galleries?