With FM2010 now using football terminology for player roles, such as Deep-Lying Forward or a Poacher, if you read TT&F 2010 you will realise the importance of player's roles inside a team - a fullback cannot play FC, but a DC could play central defender, ball-playing defender, etc..
Questions could arise; how can I train my full-back so he becomes the perfect full-back? How do I make my highly talented 17 year old become an excellent wing-back? etc..
Just as a basis, I will paste what each training category trains:
StrengthNatural Fitness, Stamina, Strength, Work Rate
AerobicAcceleration, Agility, Balance, Jumping, Pace, Reflexes
TacticsAnticipation, Decisions, Off The Ball, Positioning, Teamwork
Ball ControlDribbling, First Touch, Flair, Heading, Technique
DefendingConcentration, Marking, Tackling
AttackingCreativity, Passing
ShootingComposure, Finishing, Long Shots
Set PiecesCorners, Crossing, Free Kick Taking, Long Throws, Penalty Taking
Now, let's see you want to train a wing-back to expertise, you're not going to assign him high shooting training because that isn't his role, but how do we know what to exactly assign him to train?

This image shows what I am building, a theoretical-based tutorial on how create a player that is perfect in his role. Upon completion of most roles (deep-lying forward, trequiartista, box-to-box midfielder, etc)
I will upload images, word-processed documents and of course, my specially crafted training files. This will of course, all be free - and I encourage sharing files so others understand FM10 at a better level.