A good meditation group is one in which there is a sense of group support, like a family. A bit of friendly competition is alright as well, we can see who can sit the longest! It is also a place to ask questions of a teacher and compare notes with our peers. In order to avoid boasting and unhealthy competition, questions within the group should be asked in a general way, not in a personal way. Personal questions are best kept for an individual interview with a teacher. The other aspect to avoid is gossip. We should keep the personal things shared by our spiritual companions to ourselves and only talk to the teacher if we are concerned and worried about something.
Ideally there should be a strict adherence to the five precepts within the group. This is a chance for people to try these out if they are not yet committed to these in their lives. Keeping the precepts is something that creates a stable foundation upon which a committed meditation practice can be built. And moreover, the precepts can keep a group free of unfortunate dramas!
The benefits of a group are underestimated. It can be great to find someone you can call and talk to about your practice, for example, someone with a similar inclination in practise or who is in a similar life situation, especially if you become a contemplative as well as a meditator.
I offer this for your reflection