Searching for Players

As you know, in FML homepage, SI provided the very useful book navigation for beginner (Link: http://manual.fmlive.co.uk).
I can say that I learn from it a lot from the start. The most important thing you have to do once you are in-game is how to select a good player and fit the position that you want him to play. As a result, SI tells you how, yes. But they didn't hand you the full list of the requirements attributes.
According to FM09 and FML, here is the full list that you need to know when choosing each players:

Goalkeeper:
All required GK's attribute better be higher than 15 except Eccentricity and Punching must be lower than 10.
The MUST have are: Aerial, Jumping, Handling and Reflexes.
The less important are Kicking and Throwing.
You don't need Eccentricity or he'll act like Higuita with Scorpion Kick or Colorful Shirts like Campos. The less Eccentricity he has, the more concentrate he is in-game. Punching ball is never an useful skill for GK. If he punches too much, the ball will mostly fall out and give chance to opponent players to score goals.
(Example: Cech, Buffon)

Right/Left Defender:
In Defensive formation, A Left or Right Defender must good at Tackling and Marking. He also has to be fast so he can chase down the opponent wingers. For Attacking formation, Right or Left Defender should have Crossing skill so he can provide ball to attacker as a winger. In Attacking formation, Right Defender acts like a Winger Defender.
The MUST have are: Positioning, Taclking, Acceleration.
Other than those are: Pace and Crossing.
(Example: Lahm, Evra, Ashley Cole)

Center Defender:
A good defender must be good at Tackling, Marking and absolutely Heading, Jumping. If he has Pace + Acceleration, he'll become a very solid wall to every striker.
The MUST have are: Jumping, Heading, Tackling and Marking.
Other than those are: Determination, Decision, Position, Acceleration, Pace and Strength.
(Example: Rio Ferdinand, John Terry, Puyol)

Defensive Midfielder:
This postion requires most of the attribute because the DMC must be good at Defending and Attacking (Support the Attacker Players). So basically, the DMC requires DC and MC attributes.
The MUST have are: Decision, Anticipating and Tackling.
Other than those are: Marking, Heading, Passing, Determination, Work Rate, Strength and Jumping.
If DMC has Pace and Acceleration, he'll become a perfect DMC.
(Example: Essien)

Winger Midfielder:
Basically, a winger midfielder must be fast and have good technique with a ball.
So the MUST have are: Pace, Dribbling and Crossing.
Other than those are: Passing, Technique, Off The Ball and Acceleration.
(Example: Giggs, Cristiano Ronaldo)

Center Midfielder:
For the MC, basically he has to be good at Passing and Creative so he can pass a ball to the attacker more often with various ways.
So the MUST have are: Passing, Creative and Decision.
Other than those are: Technique, Work Rate, Pace and Strength.
(Example: Fabregas)

Attacking Midfielder:
Just like MC but he doesn't required Strength that much. Besides of that, Long Shots and Flair are the better he has, the better he becomes more dangerous.
(Example: Steven Gerrard, Xabi Alonso)

Forward/Striker:
A dangerous striker is the one who can hit the ball fast and accuracy. If he has speed and good at heading, or can decide what position, the timing to score or shoot (Composure, 1st touch), he'll become a goal machine.
The MUST have are: Finishing, Off The Ball, Composure and Pace.
Besides of those are Acceleration, First Touch, Heading and Technique
(Example: Torres, David Villa).

This is the combination between FM09 and FML. Hope it helps you to build up a good squad!