Every little bit helps
In the group chat try also to bring people who are not speaking into the conversation. e.g. 'What do you think about subject X'. I am sure you know the tips but retain eye contact at all times and nod to encourage others. Taking notes might help especially if it is provided as often paper/pen and is provided. Do not speak with your hands across your face.
For your one to one when you get to that stage swot up on history / direction of the company, product etc. We all know these are obvious but great people still turn up and display zero knowledge about the company they allegedly want to join.