Understanding The Action Line

To create an action line you must enter Move, Scale or Rotate. You can press "W, E or R" on the shelf. Then click on your model's surface and drag out the action line. The endpoints of the line will snap to whatever is under them. Any previous action line will be removed.
Drag the outer yellow ring of an endpoint to position that end of the line. The endpoint will move in the plane of the screen.
The yellow circles will resize to indicate distance from the viewer.

To move an entire action line, click on the yellow rim of the center circle and drag it.
The line is moved in the plane of the screen. Its distance from the viewer does not change.
You can also drag the line itself to move it.

To move an end of the action line, click on the yellow rim of an endpoint and drag it.
The endpoint is moved in the plane of the screen. Its distance from the viewer does not change.
To move an endpoint of the action line to a precise place in a model (for example, to be precisely at a joint), view the model along one global axis (Shift-rotate the model so it 'clicks' into a perpendicular view) and center the endpoint properly in that view, then do the same thing while viewing along another global axis.

To Learn About Posing a Model Click Here.

To Learn About Transpose: Moving a Model Click Here.

To Learn About Transpose: Scaling a Model Click Here.

To Learn About Transpose: Rotating a Model Click Here.

To Learn About Blurring Masks and Joint Rotations Click Here.

To Learn About Transposing With Bones Click Here.