There’s a lot of writing out there on how to run a productive critique.
One of my favorites is by Jake Knapp of Google Ventures where he lays out nine rules to follow. For example, one great rule is to write it before you say it – this requires 5-10 minutes of silent time to look at the work and write down your initial reactions. It allows you to respond to the work individually – eliminating groupthink. Scott Berkun also wrote a great guide on setting up a critique and goes into the details of specific questions to ask and what materials you’ll need.