As the person getting a crit, you have a lot of responsibility for making the process valuable. Make sure that you are prepared to ask pointed, specific questions about your work — know what you want answers to, and be able to clearly ask questions that will get you those answers. Think about what you want to get out of the crit, and have a written list of questions with you. Generic questions like “what do you think?” are not very useful.
Take notes during your crit! Or, ask someone to take notes for you. Or, ask if it’s OK with everybody to record the conversation with your voice memos app if you don’t like writing. You should be getting a lot of information thrown at you, and you will need to parse it out and think about what everybody said after the crit is over.
Since you are going to get a lot of opinions about your work, you will have to decide what feedback you do and do not care about. Just because someone told you something, does not mean you have to act on it (this includes your instructor). Everything is up for interpretation — but also note that ignoring what everybody says probably won’t help your work improve.
It is helpful to understand that different people react differently to different kinds of crits, which is why if you are not getting what you need from big group crits, or one-on-one crits with your instructor, you should ask for more feedback from your classmates or friends. As a student you need to learn to pull what you need, instead of waiting for what you need to be pushed onto you. Design school is about being active, not being passive. If you need more, it is up to you to find it.
Usually, the hardest thing about critique is this: you have to accept critique without taking it personally, without getting heated, and without getting defensive. You have to approach the critique process as if the feedback you are being given is real and truthful — not as if it’s a personal attack. This is difficult to do (especially in front of a bunch of your peers), and it takes practice. Remember that all of your design heroes also make crappy work sometimes, and feedback is what helps their work get better — just like you.