Last week I reviewed student portfolios at the AD2SF review. The thing I've learned about these big portfolio reviews is that in order for your advice to be helpful, you have to tailor it to the level of each person's book. If the book doesn't have a good concept in it, there's no sense in talking about typography.
I like to flip through the whole book first to get an idea of what level it's at. I also ask the person upfront what their current situation is (which quarter in school, looking for a job, freelancing, whatever). This helps me assess what the landscape looks like. The landscape (and the discussion) usually then takes place on one of three levels:
1) Concepts. If there aren't solid concepts in the book, the rest doesn't matter. Bad concepts with good design are just bad concepts. If the concepts are hit-and-miss, most of the review will be about pinpointing which concepts are working and which still need work.
2) Execution. If the concepts are solid, I start looking at the craft. Do the executions deliver on the underlying concept? Do they communicate? Are the headlines well-written? Which are the strongest and weakest? How about the copy? For art directors, I'm looking at design, type treatment, etc. I want to know that this person has a mastery of the skills they'll need in the industry. What can be polished?
3) Personality. If the concepts are good and well-executed, I start looking for a range of voices. A smart book is one thing. A book that makes me laugh is another. And a book that makes me laugh on one page, think on another, and get all weepy on the next is another thing altogether (I have yet to get weepy over a book). I see that as the last stage--you have a good book with well-executed concepts. Now push yourself to write or art direct in different styles. Show me that you have more than your one voice.
Good luck to everyone finishing up their portfolios.