The phrase "other duties as assigned," which appears on many job descriptions, perhaps applies most aptly to the role of an administrative assistant or secretary. Ad hoc job duties are those specific to a certain situation, event or period. They are typically not a part of your daily duties as an administrative assistant but may occupy a fair amount of your workday at certain times.
When your organization or business is holding a special meeting or conference, many logistical issues will likely fall to you as the administrative coordinator. Duties may include maintaining registration lists, processing registration fees and creating name tags. You may also be asked to be available the day of the event to help with details. Everything from ensuring that the audiovisual equipment at the event is functioning properly to confirming meal requests could become part of your ad hoc duties.
Creating reports and conducting correspondence are likely duties associated with your job. At times, though, you may be asked to create special documents, such as a spreadsheet specific to a project or a letter to donors during the holidays if you work in a nonprofit organization. These documents may not be forms familiar to you, but you can find examples of most common business documents and correspondence formats online to use as guides.
The role of an administrative assistant is primarily focused on helping your supervisor do her job more efficiently and effectively. At times, you may be asked by your boss for special assistance with projects or personal matters. Helping to schedule travel plans, responding to inquiries while your boss is absent and assisting your boss with updating software or other technologies are all duties she may assign to you. These duties are often not outlined in a job description, as they arise under specific circumstances.