For your Café Sci to run smoothly and be a success, your team needs to be diverse. Try to include people with a range of interests (not just science!) and lots of different skills. Ideally you also need students from different age groups so your café doesn't grind to a halt when older students leave school.
It is a good idea to assign different roles to different people, so that it's clear who's responsible for what and the team can benefit from everyone's skills and experiences. To get all the jobs done, you'll probably need to fill the roles listed below . You could break them down if more people wanted to get involved. If you have a keen photographer, for example, this would be a great addition to the Marketing role. For details, see here.
The manager is responsible for the overall management of Café Sci in your school. They will be a leader, keeping the organisation team running smoothly.
The co-ordinator is responsible for making sure each café event runs smoothly.
The spokesperson is in charge of all the communication between the organisation team and people outside the school, for example the speaker and Project Organiser.
The success of cafés depends on people turning up and that depends on effective publicity. You will need to publicise cafés well in advance and make sure that information about them is easily available.
The reporter records what happens at the café and supplies some feedback and details to the Project Organiser to be included on the Café Sci website.
This person works on the day, welcoming the audience and speaker, directing audience questions, encouraging discussion and introducing new questions if things slow down. This is a key role and not an easy one. It may be a role for one person or you might want to rotate it around the team. The Project Organiser can help with advice and techniques for chairing.