If team interactions are weak, consider beginning a lesson by discussing the kinds of comments or questions that could be useful during team conversations for the particular activities of the day. If students understand the nature of the coming task, you could invite the class to brainstorm ideas using a Whiparound for sentence starters. Possible ideas are:
You could then post the list of student-generated sentence starters in the classroom so that students can refer to them as they work together.
When you observe high quality interactions, commend the team members and share your observations with the class.