HOW: Clear and concise communication - both verbally and with hand signals. Use of basic and consistent terminology (ie. don't flip flop between throttle & gas).
WHAT: Focus on what matters - you can't teach everything in one day and trying to would just overwhelm a new driver. Assume the student knows nothing and go from there.
WHEN: Don't say "last lap you did this", because they don't know/remember what they did - instead, give feedback immediately in the moment. On debrief focus on 2-3 feedback items max.
AMOUNT: Be cognizant of how your student interprets your instruction - is it too much, too little, overwhelming - and then adjust.