The common elements, for the most part, are described in Basics and even those change from tradition to tradition. This is a rough list of the garden of Wiccans existing in the universe. The so-called original tradition, evolved from Gerald Gardner in the late 1950s. Whether or not she initiated him into a tradition harking back centuries no one can prove. However, Gardner did indeed create a tradition that is quite alive in the twentieth century, going into the twenty-first.
Practices are similar to Gardnerian ritual.
Alternately, there is a 1734 tradition that describes itself as the American Celtic Church - the tradition itself is reported to be quite powerful, although its academic sources are questionable. 1734 Net Alexandrian Alex Sanders tried to gain admittance into more than one Gardnerian coven and all denied him, so he formed his own tradition. At the same time, he made Wicca much more accessible to the public, initiating many well known pagans and hiving off multiple successful covens. His style was similar to Gardnerian tradition with the hierarchical divisions but it was apparently easier to gain access to an Alexandrian coven. I'm under the impression that an individual must actually be British to practice this tradition.