1, Always explain to your passenger how the
button for transmitting on the radio works in
case you pass out and they need to talk to ATC
A flying instructor friend of mine passed out and
the guy having the trial lesson managed to fly
to a near by airfield and be talked down to
finals with help off ATC.
At that point my friend came around and took
over the controls and landed the plane.
He doesn't instruct any more but is thankfully still alive.