Covens

A coven is a group of witches who cast spells together. A traditional coven requires thirteen witches, but can be as little as three or four.
The coven is usually led by a high priest and/or priestess. By working in a group, the members can increase their power and perform bigger spells as well as worship the God and Goddess and celebrating Sabbats. (Pagan holiday)
Some covens or witches will participate sky-clad (naked) or wear special ceremonial robes.
Some witches prefer to work in solitude, while others prefer a coven. If you choose to join a coven, always be careful of who you are meeting up with. If you have group of friends with similar interests then it would be a good idea to form a coven with them. 
More information can be found online.