Another way to become aware of the tension in the arms is to first tense the shoulders as you keep the rest moving and relaxed. You move to the arms next and keep the forearms relaxed and mobile and than move to the forearms. The last are the fists and you need to find the direction in which to close the hand (for example bringing the fingers together from the sides as if you are trying to keep water in them) so they do not effect the forearm. Do the same with the legs as you push each others legs or push and roll a partner on the ground with just your feet and see how you can roll or screw your foot into him and give him motivation to roll where you direct.
Honest practice is understanding.