john and pa_ul have said good stuff, I would like to add:
Be positive, have positive answers ready, pretend to be confident, dress very very smartly, tell them how you would be perfect for the job, tell them why you've chosen the job out of the others that are available (i.e. you love amusement parks and thought how wonderful it would be to work in one!)
You have to mean and believe what you say, and you're best to be honest (otherwise they'll just sack you for false information!)
Everything has two sides, so if they ask you a question to make you think of negative things, always make it a positive (i.e. have you dealt with an customer who was unhappy and asking you for a refund? "No, but I know that I would need to refer them to someone who can help" ...) there are loads of answers, but if you can show that you can 'think on your feet' (fast at calculating situations) they'll appreciate and love you for it - and you'll most likely get the job.
Honestly, just enjoy the interview, maybe even tell them it's your first, smile, polite, confident, tell them your positives, even offer to go on the trial period from the job centre (I am so confident that I will be good at this job that I would like to offer myself for a trial period, it's run by the job centre, you don't have to pay me any wages or anything, but you will then get to see all my skills in action and know I am right for this position).
Use your own words, do not revise and learn other peoples!
Good luck, if you follow the advice given on these pages, you will not go wrong, you will enjoy the buzz of the interview, they will enjoy interviewing you, they will like your personality, and you will get the job.
It's simple when you got the knowledge stored, and your confidence beaming through.