Off the Ball, Pace, Work Rate and Stamina...ok that was 4. A team built around those attributes is hard to beat. I don't buy slow players (even CDs or MCs, lazy players, or players who can't go all out for 90 minutes.
Off the ball is the most underappreciated attribute in the game...not just in FM but in football! Off the ball is at least as important as passing...who cares how good your MC passing and creativity is if nobody has a sense for moving into space, let alone making dangerous runs.
Lastly, pay attention to preffered moves likes "looks to get forward," "moves into" channels" or "shoots with power."