Experience doing checkouts does help. When I started my flying career as an instructor, the large flying club I worked for insisted that every renter pilot did a 1 hour recurrent training flight annually. I did a lot of these and used the Private Pilot Flight Test report form as my training record. After awhile I started filling out the form including scoring all the in flight maneuvers before we took off based on what I had seen on the preflight, start up, taxi and runup. My initial scores for the inflight portion were often surprisingly close to what I observed as skill deficits due to unfamiliarity, lack of recent practice or sloppiness on the ground usually translated to the same in the air. However looking back at that time I did the club members a disservice by treating the flight as a test instead of as a learning opportunity
Fast forward 40 years later and I am now the safety officer at my gliding club. The Soaring Association of Canada requires member clubs to have a Spring training program but leaves the content of that training to the club. I revamped our clubs training to include a formal ground portion and an inflight portion that is the Transport Canada Glider Pilot Flight Test. The logic is that every pilot should meet or exceed the standard for the issuance of the license. Crucially, however the flights are not "tests" they are conducted on a train to proficiency model. That is if a particular maneuver is below standard it is practiced until proficiency is attained then the they move on to the next maneuver. I emphasize that there is no "right" number of flights needed to complete the spring training and even if the instructor is happy with the members performance additional practice is encouraged if the member feels that would be beneficial.
Finally as was alluded to in some of the above posts a positive attitude on the part of both the instructing pilot and the pilot being instructed is very important to achieve the maximum value from the exercise.