Here are the guidelines for what we're looking for at this third stage. This time, the guidelines are not Commons-specific, but are a set widely used for evaluating teaching portfolios. You may be interested in where these guidelines come from, and other materials the Peer Review of Teaching Project has generated.
As usual, make sure you do your review before you come to the Commons in May, as there'll be time dedicated to individual feedback and discussion.
Have a browse of some other portfolios, to gather some good ideas beforehand. Bring the URL of any you particularly like