I've been in a couple of critique groups, and from these experiences I've learned there are some things you need to keep in mind when you join a group.
1. Leave your ego at the door. No one is there to blow smoke. Members are there to help make your work stronger and more marketable.
2. If something in your work stops or bothers one or more of the group, it will bother a reader--maybe. Keep the in mind.
3. You do a good job of critiquing other member's WIP because you are there to help, not just be helped.
5. Sit on suggestions overnight, even if your first reaction is strongly negative and you don't agree.
6. Be honest about the work you are critiquing but don't make it personal.
7. Don't take anything personally.
8. If you are not getting the rigorous critique you feel you are seeking, perhaps this is not the group for you. Try another.
9. Keep your cool when others critique your work no matter how you are feeling. You can screech or cry in your car on the way home.
10. Remember that in the end it is your call. You are the author.