My students bring their own planes and we supply the buddie boxes at my club.

Once the students plane is checked out, the radio that belongs to that plane is now considered the master nad the buddy box is the slave.

The instructor takes the master and hits the trainer switch. The student then using the slave radio to verify all control surface movement and throttle movement

The plane is now started and taken to the taxi area which at this point if it is a first time flight for either the plane or the student or both then the instructor will fly the plane and get it trimmed. After that is done and the plane is taken up high, control is given to the student only if and when the student is ready. Some students just feel comfortable with the sticks on their fingers and follow the instructor while the instructor flies the first flight or two.

A dialog must exist between the student and instructor as to who is doing what and when. Even little things like looking away must be communicated so if you look away and the instructor is flying he does not hand control to you if you are not looking.

Which brings up another point. Both the instructor and student need to agree on comminucation when it comes to aircraft control before a flight is even begun and I do mean every flight. As an exampe, if the student is flying and is getting tired he should make the instructor aware that he feels tired wants to hand control over to the instructor. The instructor should then acknoledge this and then take control and let the student know he now has control.

My point is communication is key to any instructor/student relationship. Each must let the other know what is hqppening and when. Control should never be handed off in either direction without full knowledge of it happening. This includes saving a plane from near disaster. I will usually tell me students I am taking control just as I do it and then once I have control explain why I took it and did not give them a chance to argue the point. This is rare as most students know when they are in trouble and are usually glad you took over.

I know it sounds silly but it works well

I am sure others will be able to add more to this