Get to know all the people in the group over which you have leadership responsibility. Know their skills and desires. Know who can do what task and who will likely want to do what task. Leaders must be an example of the traits they expect their volunteers and staff to manifest in their duties. A good leader must also know what to ask from people and where to assign them. Do not expect a duck to act like an eagle. All of the positive modeling in the world will not change reality.
Choose wisely, and it will make you happy. It will make them happy. It will make the church happy. And you will get more accomplished! This means asking questions and listening carefully to the answers. Do not make assumptions here. Listen carefully to your staff and volunteers, and ask specific questions. Consider giving people a choice of different tasks and see how they respond. Sometimes people will agree to perform tasks that are not their first preference if they have previously been affirmed by the successful completion of a task they do prefer. Leadership is about relationship and personal fulfillment. If they feel affirmed and you have earned the right to ask because of your relationship, then they will be more willing to do more for you.