I think volunteering is always great, not just for your resume,  but so you can gain experience in the field and see what aspects of it you are interested in.

If you think you may also be interested in Library Science, you want to make sure you go to an ALA accredited school. LIS/Informational schools do not all have archival concentrations, so you also need to look for one that lists archives as one of the specializations you can have. I actually do not have much experience in the archival field,  but my suggestion would be to find an I-School with an archival concentration (like this or this) 

Looking at what professional organizations like SAA recommend will probably also be useful. 

I hope this helps! Good luck! 

Congratulations on graduating!!!! 

Based on my experience, here are the things that you might want to look for:

1. Choose an ALA Accredited school
2. Choose a school with a strong internship program, or make sure you get a internship/job in a library while you are in school. (This helped me figure out if i was focusing on the kind of librarianship I actually wanted to do when I graduated.) 
3. What kind of librarianship are you interested in?  Do the schools you are looking at have a focus on that? 

• Do you want to work for a University, Public school, Public library or Corporate library? 
• Once you choose what kind of library you want to work in, what do you want to do in that library? Do you want to work with the public (so you might be a Reference, Instruction, Teen librarians, etc.) ? Do you want to work with resources (cataloging, electronic resources) 

 I hope this helps! Good luck! 

Thank you!