• Do not hold back. If you are the only one in the group who is bothered by a scene, passage, etc., say so, even if you are in the minority. It could possibly be that you misread the author's intent or you could be presenting a real problem that everyone else has overlooked. If one reader is confused, that's too many. Give your feedback in case the author can better clarify. But also be prepared to give suggestions on how it could be clarified, which leads to the next point.
• Do not puff up like an old toad and refuse to comment. In other words, check your ego at the door. If after you give your opinion, and the author and others still don't agree, then respectfully say, okay, it's your call. Avoid comments such as, I'll just sit here alone with my ignorance and shut up, or, It's probably just me because I am so worthless. I call this Martyr Mode. It works wonders on kids. But during a critique, try to avoid it at all costs. Simply agree to disagree because varying opinions make the world spin and this does not make you a dumb person or your opinion not valued. And wipe that frog look off your face.
• Do not go into attack mode and rip someone else's work if you've received a tough critique. We are only human, and being attacked will undoubtedly create defensiveness. If you've ever been on the receiving end of an all out verbal assault, I don't have to tell you how hurtful this can be.
• Do not overlook the positive. Yes, this can be hard if the material isn't working at all for you. But find something nice to say to the author, even if it's nothing more than I like your hero's uncle, Joe Bob or I admire your heroine's guts when she wears those pink socks.
• Do not mess with someone's voice. This can be touchy, especially if you feel like something needs to be worded better. In my opinion, the best way to handle this is to mark, Confusing, rework, then add a question mark. Question marks can be your friend. This denotes that you are acknowledging the work is not yours and that you're only making suggestions. Again, it's the author's call whether or not to change it. There's nothing wrong with brainstorming a list of possibilities, as long as it's the author who makes the final decision.
• Do not do extensive line editing unless you are a) qualified b) this is the final manuscript before submission c) you enjoy doing this and the author has requested your help. Yes, by all means, grammar is very important and you want to point out those nasty typos. But as a whole, most writers have a good grasp of proper English, or should. However, fiction writing is not always about proper grammar or sentence structure. It tends to be about the story, motivation or lack thereof, good characterization or lack thereof--- well, you get the picture. If you have a partner with serious grammar problems, tense problems, etc., suggest a book or a course. If you are on a more advanced level, time spent trying to teach grammar can lead to resentment on your part. Unless you live to line edit. If so, please contact me.
• Do not run over your partners and insist your way is better, you know what is best for their story, etc. Suggesting is one thing; strong-arm tactics are another. Your partners may come to the next session armed, if only with plastic utensils for protection.
• Do not defend your work to the death with a diatribe that makes your partners ears ring. You may believe every blessed one of them is wrong, but it's amazing what happens once you go away and think about things. Feel free to calmly explain your intent, but if you're too tough in your defense, then you run the risk of alienating your partners and in turn, they will fear you but more important, they might no longer give their honest opinions.
• Do not LET your critique partners totally run you over, especially during brainstorming. If they suggest an element in your story that you're not comfortable with, then speak up. This will help to avoid re-plotting the same book again. Of course, you should be allowed to change your mind if it sounded good at the time but didn't work out after all. But if you realize from the get-go this is not your vision of the story, by all means, say so, and save a lot of grief.
• Do not revisit the same path over and over. In other words, do not keep submitting your first chapter to your group unless you've totally rewritten it. Make the changes, put it aside, then go forward to chapter two. Your critique partners will more than appreciate this. After repetitive viewing, even fresh eyes become immune to problems. If you wish someone to read the manuscript later in its entirety, they can pick up mistakes in early chapters at that time. Chances are, you may find that changes are necessary to the beginning of the book once you've reached the end. Have faith in yourself and your abilities.
• Do not forget to thank everyone for their input, if not during the critique, then afterward. People like to know they're appreciated, no matter how small their contribution.
• Do not overlook human nature. If you have an out-of-sorts partner during one session, give them another chance. Life may be stepping all over them, and it's natural for people to sometimes react in ways that are out of character. However, if you have a partner who continues to exhibit disruptive, destructive behavior, someone needs to talk to them. If worse comes to worse, the group may be forced to ask that person to shape up or ship out. Or the whole group could relocate to other areas of the country.

Critiquers Creedo:
Be open and positive, embrace good solid suggestions, give as well as receive, be kind and honest, nurture when needed but resist the urge to spoon feed lest it lead to a diet of dependence. Above all, be true to yourself, your books, your partners and if in the end an editor declares none of you were correct, voodoo is not an option.