That said, accepting criticism is difficult for the best of us. I myself have a very hard time with it. Of course I recognize that my manuscripts need work, but when you've put so much effort into one project, hearing other people tear it to (metaphorical) pieces is a lot to handle. My critique partners are wonderful; they hit the perfect balance between critical and appreciative. They list the things they liked, the things they didn't like, and how improvements might be made.
Some tips for critiquing:
~Be honest, but not harsh. Start out by talking about the things you did like, then list some negative aspects, then finish with your favorite part of the manuscript.
~Offer up suggestions to fix the problems you identified. Even if the person you're critiquing goes in a different direction, having suggestions can help get their creative juices flowing.
~Brainstorm! Talk about the problems in each person's manuscript, and try to get to the root of the issue. Is a character acting strangely or in contradiction to their previous actions? Is there a pacing problem?
~Don't go with your immediate reaction. When someone critiques your work, take a few minutes to think about it. I objected to the idea of changing my manuscript to first person when my editor initially suggested it. However, after a few hours of considering the story and my own notes, I realized changing it to first person would make the story much better.
~Just remember, even if critique sucks now, you'll be grateful in a few weeks when your manuscript is a million times better.
Now go out and find yourself a critique group!