[euromodder]

late 1980s, or 1990s Toyotas or Hondas 5-speed would be fine.
Reliable, easy shifters.
Normal pattern, i.e. no pushing or levers to pull for reverse.

Warm up the engine and transmission before taking on a student.

Start teaching at standstill, engine off, just to give them a solid idea of where the gears are.
No looking at the stick !
They should know what gear it's in by feel alone.

If you want to avoid the problems Metro mentioned : learn them to shift with their fingers on the knob, hand above the stick.
NOT with the palm of the hand resting on the knob, nor with the hand turned vertically and the fingers clamping around the stick.
With a good and warm box, hardly any force is necessary to shift.

Teach them to not really guide the stick themselves.
It knows where to go, it just needs a little nudge in the right direction.

1 to 2 is only some light backward and sideways pressure.
2 to 3 is only some slight forward pressure - the stick will center itself while passing neutral and line up with 3rd gear.
3 to 4 is only some backward pressure.
4 to 5 is forward and some light pressure to the right.

Sounds obvious, but it works way better that trying to follow the shift pattern with decided hand movements.