heavy training schedules in either fullback, central defender, goalkeeper, box to box midfielder, inside forward, complete forward and not sure for amc, perhaps just amc their. decent class of coaching staff (close to 5 star training regime you can get) try to get the best training facilities (or loan the youngster out to a club that has top training facilities if you do not). If the player is 16-17, let them have 5-10 minutes of game time on the pitch every now and again, if the player is 17-19, let them have up to 20 minutes of game time. The reason for this is because you do not want them to "burn out" as in, peak too soon and their stats drop prematurely.