I've always held the belief that Jesus and his 12 mates were a coven. Jesus was a healer, such things were associated with witchcraft. I have even read that there's the possibility that during his 'missing years' that he trained with the druids. Either way Jesus certainly did some magickal things, he communed with the devil, angels, God and exorcised spirits. Things a lot of modern high magicians do today. He was also Jewish and so was probably taught the qabalah.
Of course I could be completely wrong.......
You may like to do a ritual once the coven has been established were you pledge an oath of secrecy (magick work is meant to be private.) and then do a blessing. There are no rules other than enjoy yourself and trust each other. I have practiced with others, I prefer solitary work myself I tend to have my unique way of performing rituals.......I go with the flow.