1. Try to make the 'applicant' relax. E.g. - "On the first leg I shall act as an intelligent passenger. So if I see another aeroplane I'll tell you - but I won't ask silly questions. Just tell me at some stage when we'll get to the turning point; if we get off track just describe what you're doing to get us to where we should be going - amd tell me if you change our ETA. Oh - and please wake me up if I start snoring."
2. I always try to finish with the low go-around - "Oops - a herd of goats has just run out in front of us!" Then "OK - that was fine, my turn now to pinch the landing whilst you stop sweating!!"
3. The debrief has to be quick for a successful PPL Skill Test because the applicant will be too relieved to listen to endless waffing. So a bit of levity - "I'm not signing anything until you get the coffees in!", then go slowly through the PPL paperwork whilst the applicant comes back down to earth. Finish by quickly summarising the flight, then a final check of any outstanding paperwork (e.g. his/her personal logbook)
4. Let him/her know that he/she can fly as P1C but without passengers until the CAA send back the licence - then give him/her a quick reminder about recency and re-validation.
For a partial pass, be as sensitive as you can and stress that it won't take much to finish things off. NEVER use words like "You struggled and barely scraped a pass, flying obviously isn't your forte......" If it was that bad be honest - it cannot have been good enough!
Am I just lucky or what? Only a tiny fraction of those I've taken on PPL Skill Tests haven't passed. Or perhaps it's just that our FIs are really very good indeed?