I think with every project team it's always important to first define the project and start with the project goal. You have to be very sure about what the project needs. Then you need to select people based on a mixed skillset. In other words, a good team member has the necessary skills for a project role and they have a good attitude towards it like if they are responsible or if they communicate well. Good project teams are balanced so a mixed skillset that showcases members' different strengths help make the team more well rounded. Of course, a good team has members that are responsible and can communicate well and often. I think all of these things work towards forming a good project team. I think a mistake to avoid is that even if someone knows what they are doing, they might not have the right mindset or the right attitude towards the project, so you need to recruit people that have a good skillset and a good attitude.