First off:
Rebels=Assassins=
Freedom and unified, but separate
Renegades=Templars=
Order by force and a single unit

But they aren't set up the same way. The Rebels are set up like the military. The Renegades are set up similarly to the Templars, each person has someone specific who taught them the basics (sometimes referred to as masters or mentors) and there is a Parliament that makes decisions.

Getting into the Rebels and Renegades:

The Rebels start off with giving the person the basics of the rebellion. Then they move on to a fake base unless the person is injured. If the person causes an ambush or something, they'll obviously not be a part of it. Next there'll be a fake solo mission, and if they pass, they're in. (Note: They will not know it's fake and the mission can be almost anything, depending on the level of trust and what is associated with the applicant.)

For the Renegades, it can be a family thing or something similar to the Rebels, but with a more violent mission. Sometimes it's by force, but get permission from the character's user first before you act all forcing.

So, those were a couple questions I've had already. If you have any, ask here, unless it's about tech, then go to the tech page.