Courtesy of rashidi1 in the FAQ at the top of the forum:
What are the important attributes for each position
Goalkeepers - Vital Skills
Positioning, handling, command of area, agility, stamina, jumping, reflex, strength, decisions and aerial ability
Other
Throwing, pace, concentration, composure, bravery and anticipation
Centre backs - Vital Skills
Positioning, jumping, tackling, marking, aggression, strength, bravery and heading
Other Skills
Stamina, anticipation, determination, pace and acceleration
Fullbacks
Choose well, easily the best position to exploit in the game. If you can have the best of both worlds then they could be the
diff between winning and losing. They can be both defensively good and offensively awesome. Pace isn't a crucial factor, but if you want them to be good defenders, then positioning and anticipation may have to be introduced as well.
Vital
Work rate, stamina, teamwork, decisions, positioning and acceleration
Other Skills
Determination, strength, crossing and dribbling
Defensive Midfielder
Holding players who can help draw out the opposition, they can also play deadly killer balls and work very well with AMC based formations.
Vital Stats
Tackling, strength, aggression, marking, stamina, work rate, teamwork and decisions
Others
Pace, passing, acceleration, determination, concentration, creativity
Attacking Mids
Link players with DMs or with regular MCs. If you place FWR often on them they could drift out of position so never do that. Use their strengths. This can be an interesting area, what's listed are bare essentials,but if they have good dribbling skills they can be very deadly too.So adjust their instructions based on what they have..you can use dribbling for long shots as a trade off.
Vital Stats
Decisions, Creativity, passing, off ball, technique, finishing, work rate
Others
Stamina, teamwork, flair, long shots, pace, acceleration
Wingers - Vital Skills
Crossing, creativity, dribbling, pace, acceleration, tackling, balance, technique, passing
Others
Finishing, long shots, teamwork, work rate, off ball
Forwards - Vital Stats
Creativity, flair, finishing, off ball, dribbling, passing, technique, pace, acceleration
Others
Teamwork, flair, balance, long shots, anticipation, crossing
Strikers - Vital Skill
finishing, off ball, jumping, heading, anticipation, technique
Other
Pace aggression, acceleration, strength, long shot