Well first things first check out aviation interviews.com. Beyond that show up, don't be cocky, it's a personality interview more than anything else. When they ask for stories don't make them up, they can see right thru them. If you have time buy the book "Checklist for Success" by Sheryl Cage, it's around $20-$25 shipped. The questions in there are great and get you thinking. It's even good prep for interviews at the majors.

An example of a question would be, "tell me about a time you had to make a hard decision". "Tell me about a time you did something unsafe".

With everything, even something negative, it's OK for you to admit a mistake, the important thing is what you do now because of it. Of course, don't make every story about a mistake you made.

Have a good range of stories, look thru your logbook remember your past flights end events. You want a base from which to draw upon.