Be professional: Be professional in how you dress, speak, and don’t forget to get to the interview 15-20 minutes early so you can collect your thoughts before the interview.
Be social (within reason): Make sure to acknowledge the other interviewees, you don’t want it to seem like you’re rude and disregarding them!
Listen: Don’t zone out when the other interviewees are talking, it’s easy to do, I usually end up getting lost in my thoughts when other people are talking during interviews. You also need to listen to the other interviewees’ responses so you don’t repeat what they said.
Sit still: From personal experience, from a group interview I participated in, we sat in twisty office chairs. The other interviewees were on my left and right, it was distracting when I would twist the chair toward them, so keep the chair stationary and simply turn your body so you don’t distract anyone.
And girls you should know this, but don’t cross your legs at your knees, just cross your ankles.
Make eye contact: With the interviewers and fellow interviewees, it shows you are interested and have basic social skills.
Don’t dominate: You need to have strong answers, but you don’t have to answer each question first, it looks like you’re overwhelming. Most group interviews have questions that are usually asked to each individual, so you don’t have to fight over answering each question but just in case.