When you’re going to a career fair, I think it’s important to have a good idea of who you are and what your skillset you possess. For the most part as a recent college grad you’re not “uniquely qualified” to be an editor, and that’s perfectly fine: job fairs are (usually) held for people who are just coming into the job market!
Be honest on your resume. Share skills that translate to your desired field. Be confident, yet gracious and take the time to listen. The goal of a career fair is to get your foot in the door and make a great impression; it’s not the time to ask a million questions about benefits, perks, or what the job can do for you.
It’s also important to understand the industry. If you want to work in print, read up on the publishing industry; for web you’ll want to understand not just the editorial side of the publishing industry, but a little about the business side as well.
You’ll also want to continue to keep yourself marketable because the industry changes quickly and, more likely than not, you’ll find yourself in positions where you’re approached by other publications. Being marketable is more than simply staying abreast of what’s in your industry. You’ll want to develop and establish a web and social media presence, engage with other people in the industry, and take on speaking and volunteer engagements. Publishing executives look closely at these things (strange, right?) and tend to favor people with a “name” because it shows they have the ability to develop relationships, meaning you will be able to solicit writers and manuscripts that are in demand.