Player development is a cornerstone of Career Mode. Assign individual training plans to your players to improve specific attributes. Focus on developing young, high-potential players (indicated by their 'potential' rating). Utilize the 'Development Plans' feature to change a player's position or role, unlocking new possibilities for your squad.
Regularly check player form and morale. Happy players perform better. Rotate your squad to keep everyone fresh and engaged, especially during congested fixture lists. Don't neglect your reserves; they can be crucial for cup runs or covering injuries.