While you may think that the person is irreplaceable—great energy, a winning personality, loved by co-workers, clients and donors, alike—every transition offers opportunity. Therefore, do not rush to fill the position until you have analyzed the tasks performed and responsibilities that this great person had.
You might be able to reassign some of the work to others to play to their strengths and relieve them of tasks for which they may not be well-suited.
Then, review the department or agency to determine what still need to be assigned. Perhaps you can define the position differently and derive an unintended benefit.
Now, you are ready to write a position description based upon the new set of responsibilities that you and your team have designed. It is especially important that you articulate the specific qualities in the new hire that you desire so that person will fit in with the culture of your organization.
At this point, start thinking ahead to the interview. If a candidate were sitting in front of you, what would you expect to see? You might interview the current employee and any employees with similar positions. What are their backgrounds and education levels? What skills and interests do they find essential to their position? What would other like to see in their new colleague?
Now you can start the search with confidence. Just remember, the more up front and clear you are about the position, the expectations and the exact duties the person will perform. To state it another way, the more you know what you are looking for in your new hire, the more likely you are to secure the right person for the right job.