Some things I've noticed:

• No dog-piling. When one reviewer makes a comment, we don't all make the same comment to show how smart we are.
  
• Liberal praise. We usually see comments about parts that work well in the same review as other parts that don't work.
  
• Relevant perspective. Reviewers are not indulgent parents encouraging a precocious child. If the fragment draws us in and showcases professional quality, we say so. If we see problems, we mention those, too.

When I write with the Hatrack forum in mind as "First Reader," I do my best work.