I lead teams in my career from 8 FTE up to 60 FTE, and the motivation is usually deferring from the position and grade of the employee. But in general every manager should know their employees and have the interest in their personal and career life. When you understand what is driving employee you can in the limits of his job role coach him and give him the assignments that are closer to his goals and interests. Don't underestimate your employees and challenge them since nobody enjoys the routine day by day, and people want to be busy even if this does not seems on the first glance.
And as their manager you should lead by example since people appreciate if you are not just delegating but as well join the team and work with them as one team.