Step1)
Creating the Control - create your control object with its up axis being the same as the twisting axis of the joint it is to be oriented to. So here the twist axis or the axis that points to the next joint in the chain is X so the nurbs circle which is the control object is created with its normal axis as X. Now rename your control object.
Step2)
Creating a Group - select the control object and group it by using the command
ctrl + g. This will create a group and parent the selected object (in this case the control object) under it. Now rename this group appropriately as well.
Step3)
Creating Constraints - select the joint and then shift select the group of the control object. Now
Point and
Orient Constraint with the same selection with
Maintain Offsets unchecked. This will take the group and its children object to the coordinates of the selected joint and give it the same orientation as that of the joint.
Step4)
Cleaning up - now in the Outliner find the group and delete the
Point and
Orient Constraints that were created in the previous step since they were only required to position and rotate the controller correctly.
The controller is now ready to be used.
By using a group node above the controller, the control object does not get any translation or rotation values as these are stored with the group node. The controller's channels are remain clean while still being in the correct position.
Get a MEL script to orient control to a joint in maya
http://tutnuts.blogspot.com/2010/03/orient-control-to-joint-mel-script-maya.html
