The easiest way to create and organize your own study group is to form a group with whom you share the same motivation and purpose. Students tend to choose the one that they are close too: their friends in class. However, it is not advisable to have your friends as your study buddies if your friends are not as enthusiastic as you or if you and your friends do not have the same goal or objective in studying.
The group need not to be very big, as 3 to 6 study buddies are already enough and for me, it is much better compared to a group that has more than 6 members because the smaller the group, the easier it is to organize and to stay focus.
Set a specific time and place where you and your group could meet and discuss. And most of all, since you are the one who is organizing the group, see to it that you prepare an agenda so that your group will be more organize. Set a time frame so that everybody in the group would know what to do and when to do it. You should also seek their opinion about leading and moderating the group. Discuss whether group leadership will be rotated or permanent.
Read here for some tips on how to have a succesful study group.