Going on a job interview is just as much about you interviewing a prospective employer as about them interviewing you. Still, there are key things that any legal employer will hit on during interviews for any level of employee, and which you need to be prepared for. I've worked for enough different firms, attorneys and managers over the years to have picked up on the right things to say, and the right way to say them.
Above all, honesty is the key. Honesty with some mild wit or a smile usually goes over well. (If they don't seem to have a sense of humor whatsoever, RUN SCREAMING. Firms without a sense of humor are not going to be a healthy place to work.) If the question comes up, be honest about having made some sort of mistake, and how you went about correcting it. But remember, any skilled interviewer has a sixth sense for BS.
Emphasize your ability to communicate. Probably the most important skill one can have as a Paralegal is effective communication with everyone: Attorneys, other paralegals, the Courts, support staff, vendors, etc. Poor communication is the root cause of so many problems we encounter. Anyone interviewing you will certainly understand and respect that communication is key to being effective in this job. Certainly any Paralegal with even a little experience can tell stories about how good communication has saved your butt, and bad communication has caused migraines and/or ulcers.
Also make sure they show you around during the interview, and ask if they don't offer to. If you might be spending a third of your life somewhere, it's important to know whether you'll be comfortable. Also, you can sneak a look at the faces of prospective co-workers and gauge whether they seem happy, content, overworked or zombified.
Most firms have a website these days. Paralegals do research, so do research on the firm both through their website and legal news sources. Check out the attorneys in that office, and their backgrounds. Dropping some hints that you looked into them before walking through the door shows that you are prepared and makes them less wary to do a "sales pitch" as opposed to a real interview.