The 2001 Rig is currently the default rig for use with Animation:Master.
There is a lot of information on the rig available to help understand the principles of rigging and to study for those times you may prefer to roll your own solution.
Introduction to the 2001 Rig
Setting It Up for the First Time
Preparing The Rig for your animation style with drag on poses.
Applying the 2001 Rig to Your Models
The different animation controls of the setup
Adapting the Rig to your models
Certain things you can do to place the 2001 setup on your mesh.
How the System Works
Constraints that make the system behave properly
Note: You will have to adjust for changes in the A:M Interface since the 2001 Rig was first documented.
The Art of Animation:Master Exercise 13: Show Some Backbone demonstrates how you can transfer the 2001 rig into your own model. The exercise uses the Boneless Thom model that can be found on your CD.
There is also a video tutorial version of the exercise available online:
Exercise 13: "Show Some Backbone"
web (21MB) zip (20MB)
One important thing to consider when rigging is what (if any) reusable actions may be available for use with the rig you intent to use. If building your own rig you may want to create some specific actions for the purpose of reuseablity.
With the 2001 rig there are a select group of actions available.
More can be read about reusable motion in the Reusable Motion Forum
I have only a basic understanding of rigging of characters primarily with experimenting with the referenced documentation and associated models above.
As such the 2001 Rig is a great interest to me and seems to me a good place for any beginner to start. For some, the 2001 rig may be all you need to complete your character animation.