When you're applying for a new job, experience counts. Even if you have some special training as an administrative assistant, a prospective employer's ideal candidate is often the person who has done a similar job somewhere else. If you have experience with certain tasks, hammer the point home by including those tasks on your resume.
You've probably heard that your resume needs to be tailored to every job for which you're applying -- and that certainly is true for the "tasks" section of your resume. First, look over the job listing and try to pick out the tasks the prospective employer wants you to complete. Then look at your past jobs -- which you likely already have listed on a resume -- and recall when and where you've completed tasks that are similar to the ones required in the new job. If you don't already have them listed, include any similar tasks with the job title, company and the dates you worked there.
Professionals who require an administrative assistant often need help with file management. Whether it's a doctor with a lot of patient records to file, a lawyer with many case files and supporting documents to organize, or a professor with many research artifacts, admin assistants help to keep the files manageable. If you have this type of experience, include it on your resume. Describe how you helped the office stay organized and include the names of any computer programs or filing systems you used to complete those tasks.
Some admin assistants do more than just file that mountain of paperwork -- they also turn it into cohesive documents that can be used outside the office. If your other admin jobs have included transcribing patient notes, preparing legal papers, creating newsletters or other writing that went out to the public, include it on your resume. While it's always good practice to keep your resume free of errors or typos, it's especially important when you're including a discussion of writing tasks on your resume. If you can't get it right on your resume, the employer may doubt your ability to keep your work-related writing error-free.
Administrative assistants are often responsible for maintaining the smooth flow of the office and making sure that guests feel welcome and comfortable. This may include making coffee, getting supplies for clients or guests, or ordering equipment that makes the office run smoother. To know what's needed, they'll need to communicate well with staff and guests. As such, people in this role need to have "soft skills," such as friendliness and being able to talk with people. Demonstrate this on your resume by including "communicator" words to describe those tasks, such as "communicated with staff about their equipment needs," or "maintained good relations with guests and delivered supplies they needed."