The problem with the landing is that a student won't learn unless you let him/her make mistakes - landing mistakes can be expensive!
I started my instructing career on gliders, and they are the hardest aircraft on which to teach landings -not withstanding the lack of the go-around option. The technique I developed (and I didn't necessarily get taught this myself - as with a lot of gliding instruction in those days it was a case of learning by trial and error) was to ensure that they knew what the landing attitude was and to make sure that this was imprinted on their mind. With the type of glider that sits on it's nosewheel/skid, you have to physically go to the tail of the glider and pull it down with the stude sitting in the front seat to demo this on the ground. After this, it's down to him/her getting the flare height correct. For the high case, a "I have control" to prevent a hard landing is not a rush. For the late/low case, the judicious 'quick snatch' is the best method IMHO.
The next aircraft I instructed on was the Chipmunk, the techniques were similar to gliders as most gliders are essentially tail wheel types - but the Chippy was a lot stronger and you could allow the stude to make more mistakes.