When completing your resume, I suggest sticking to educational or professional experiences that apply to the job.  Proof read your resume multiple times to ensure you aren't using any offensive language or providing information about yourself that is overly personal and does not apply to your professional credentials.

Career fairs are still a valuable activity, especially for positions that are available in large quantity for projects or initiatives that a company is implementing. Many times, attending job fairs can be about your future connections and opportunities, not just the immediate job opening. The key to having a successful experience at a job fair is being very targeted in which companies you visit with and what you do with the information and contact information later. One aspect of a job fair that you don't get online is the opportunity to impress people in person. That is a drawback of the online posting process, so if you are someone who does well presenting themselves in person, then you would want to take advantage of this chance.

First, set up an end of summer review meeting with your HR contact. During this meeting you can cover your accomplishments, discuss your overall experience at the company, inquire about winter break opportunities, and end the meeting by expressing your interest in continuing employment the company.
Second, if there is a particular work group you are interested in you could try to do a job shadow or lunch meeting with the director/manager over the group. (At our company we encourage this experience but you should proceed with caution or ask your supervisor if it hasn’t been done before at your company.)
Third, if there are employees that started as an intern and converted to full-time you could ask how they made the transition.
Finally, when you return to school be sure to visit the company job posting board and search for any positions you want to apply to. Once you find a position (or around early-October) you should send your updated resume to your internship HR contact. If they do not have any positions available at that time do the same thing a few months later. Keeping your name on their radar may help land your first job. Good luck!

HR has several areas which are fairly easy to enter, one being recruiting, such as working for a recruiting agency.  The other is analysis work in Benefits or Compensation, both which tend to offer entry level roles with little experience.  The third may be a support role for Training and Development.  Look for jobs in non for profits, or Associations, or Universities...as well as large Corporations.