It is nerve wracking basing your entire future on something that may be over in the first ten minutes!
Then it's the candidate's whole attitude during selection. There are, in my opinion four categories of candidates.
1) those that get themselves noticed for being enthusiastic workers, and volunteers.
2) those who are not enthusiastic and just coast along
3) The grey man who does not get noticed at all. He gets on with is work without need of supervision and occasionally volunteers.
And 4) The right combination of 1) + 3). Not hopping up and down waving his hand in the air every time they are looking for a corvée chiotte. Friendly with his fellow language speakers but not forming a clic. Gets on with his job without going over board.
Then it's down to the tests. Physical we have all been through. IQ, putting the square peg into the square hole, 2,4,6, ?, 10 etc. These questions can be found and studied on Internet.
Then it's the dreaded 'gestapo interrogation' Au secours ! Do NOT change your story.
Teeth and Medial have all been gone over.
The Psy, again be natural and do not change you story.