The first thing to do is realize that even though it is at an Amusement Park it is still a JOB. So you need to treat it as such.
Be sure you are ON-TIME, planning to get there 10-15 minutes early would even be better. Dress in "Business Casual" at a minimum. So that means things like t-shirts, jeans, shorts, tennis shoes, sandals are a big NO. Doing just these two simple things will often put you ahead of a good portion of the people interviewing.
In the Interview be positive and upbeat. You may or may not have a group interview. The biggest issue here is answer as YOU would, not as other people are answering as they could be wrong. They will most likely ask you about your previous work experience, if you have none then you could talk about your school and/or any volunteer work that you do.
They may ask you about your strongest and weakest attributes. It is the weakest that gets a lot of people. So the key is to try and even make your weakest point a positive.
They may ask you about how you would handle particular situations. But they also know you don't know their policies so they are really looking for how you handle the question not necessarily the right answer. Of course if they asked you something like how would you handle a lost kid and you said you would tell the kid good luck you will never see your parents again..they may have a problem with that.
They may ask you where you would like to work. So think of a few areas you may like and the reasons you choose them.