Mirrors, mirrors, mirrors! He can't use them enough! My last instructor who I did the first four tests with never used to remind me about mirrors - I knew to look in them when I was indicating but that was about it. My new instructor was CONSTANTLY on my case about mirrors. Every time I brake, and that means every time my foot goes near the brake pedal I must look in the mirror first - every time I turn into a new road, I had to check in the mirror to see who was following me.....and so on - I had never had mirrors enforced on me so much and I really believed it helped as I felt like I was driving terribly on the day, but I did notice that out of nerves I was constantly looking in my mirror and I kept catching him watching me in his, so I must have impressed him with this!
Also, bit late now but my tip would be to get a young pretty female instructor. My first instructor (of many years) was a plump, older gentleman with attitude, who had been known to ruck a few of the examiners at that test centre. The latest one was a 28 year old girl and when she saw that I had been assigned to the chief examiner who fails everyone, she asked the other instructors why she always gets him - "coz he likes you ;-)" they all replied! ;-)