Hey, I don't really look at the personalities as well, or let's say it's not the main point I focus on. When I start the season, I look at my hot prospects and which one are going to be my priorities (biggest potential stars). According to me, the 2 most important things to look at are:
- the TUTOR's PPM
what you believes are the most relevant PPM to be be learned for the young player
Be careful on the ones you don't want the hot prospect to learn, like dive into tackle if he doesn't have a good mark on tackle, but he's good on positioning and should stay on feet, dwells on ball if he doesn't have any power/strenght, argues with ref (which is hard to unlearn then, and use a training %), shoot with power if he's more a technical/good flair striker, tries longue range passes if he's more a BWM and no good mark on creativity/decision/passe...
- the DETERMINATION mark
The tutor MUST have a higher (or at least the same) mark as the young player as it will decrease it if it's not the case. This mark can't increase itself with time, and is really important if you are losing a game and want your players to "fight" til the the last minute to score and avoid a lost game.
If a young prospect already has 16 or 17 in determination, and there's no senior in my squad with 17 or 18 in determination as well, I leave the young witout tutoring and prefer to teach him myself some PPM through training. I don't want him to lose any detemination and risk them as well to hate each other and make trouble in the group.
After those 2 points, I look at the tutor's age, his reputation, the same language as the trainee (if from overseas)...
The tutoring last between 4 or 5 month, so July/August til December. In January, I swap again the Seniors/Juniors (I don't mind if the tutor is DR and the trainee is AMR or MC if the PPM is/are relevant and the determination higher). The young would have 2 different tutors in a season and could learn more than 2 PPM (more than you should have teach him in the same period of time). In addition, his determination could incredibly rise according to the 2 players determination mark difference. You have to associate those things with some games entries around 60 or 70th minute in cups or easy games (around 20 games in a full season if he's one of your most important hot prospect)., and put him back in the U19/reserve squad after the game (to be sure he'll play when you don't use him.
If you follow this process, you'll be really impressed about the trainee's improvement in comparison to leave him play the full season in the junior squad with the only normal training.
Know that what I'm saying is what I experienced during all my saves in the different Football Manager, and is not based on anything official. I could be wrong in something, as other factors are important in players' development (hiden marks like professionalism, ambition, injury proneness...), but I've known some success that way.
I'd love to know other experiences too, and help us to improve as "manager"
(and become some kind of Wenger/Ferguson...)