This question was recently posed in a chat room I was in. Because of the limited response it got, I decided a more in depth explanation was required.
First thing's first. Do you want to be published? If so, you have to develop a tough skin. You have to be able to take as much constructive criticism as you're willing to put out.
Many people are at different stages with their writing, so you may need to test drive a few critique partners before finding a good match.
Start out with a few basics. Communicate your goal, your genre, what draft you are on, and what you hope to gain from your critique partner. Exchange a small amount of work- the first page or two. With this type of preliminary run through, you can get a good idea of your potential CP's style and feel out your compatibility level. Do not commit to exchanging chapters until you've established this.
You put a lot of trust and value into your CP's feedback, so it is well worth the trial and error to find the right one/ones.
A few qualities that are helpful in a CP:
- Honesty- yes you can give/receive honest feedback without being cruel
- Attention to detail- your MC's eye color changed from ch 1- ch 5...they need to recognize this
- Good grammar-
- Promptness- if you agree on a chapter a week- stick to it
- equivalent goals-
- same stage in your WIP
- write in the same genre as you- if not- make sure it is a genre that they actually 'like' reading
Good luck and as always...happy writing!