A good practice for an interview is to set a time when you get home from school EVERY DAY, and have your parent(s) sit down with, 2 chairs facing each other, and have them ask you questions about your day. What did you do in math today? How did (Sport) go today? etc. If you want to practice during the summer, do the say thing, but have your parent(s) sit and ask you questions about whatever you did during the day.
Practice sitting still. Practice looking them in the eye when you answer. Practice NOT saying Like, Um, Ya Know, etc. DON'T try and anticipate any questions you think your ALO/BGO might try and ask you.
a) 99% of the time, we don't really care what the answer is. We want to determine YOUR POSITION on a subject. We want to know you better. We want to make sure the answer you give is YOURS and NOT your parent's or "That's the way I was raised".
b) If you think you're LUCKY enough to actually get a question that you've been practicing, then your answer WILL SOUND PRACTICED. Thus, it will not seem genuine.
When people say they need practice interviewing, what they REALLY NEED is practice with "Public Speaking". Just dedicate 10-15 minutes a day. Preferably when you get home and before dinner. You can basically answer 4-5 question about how your day went. You can concentrate on your body language, confidence, diction, enunciation, and not using dead words like "Like, Ya Know, Ummm," etc. If you can practice that, then the interview will be fine. And while I can't speak for whoever is going to be your ALO interviewing you, I can say, that if I was interviewing you, there would only be a couple of questions that I would ask you that you could even possibly have practiced for. Most of my questions require you to dig into your past and "TELL ME ABOUT A TIME" type of questions. Which I always follow up with questions that expound on the previous question. And of course, I always ask opinionated questions that have NO RIGHT or WRONG answer to it. I simply want to see if you can think for yourself or at least have your own opinions. Granted, we are all products of our environment; and most of your values, morals, beliefs, etc. are influenced by how you were raised. But a time comes when you have to look internally at all those morals, beliefs, values, rights/wrongs, etc. that you've been taught, and decide for yourself if you believe them "AS YOURS" or if they're still part of those who taught them to you. If you've made them yours.... then great. If you've decided to adopt some new opinions/beliefs/etc. then that's great too. If your answers don't sound convincing, and they sound like something that's rehearsed or simply something that you've repeated your whole life without conviction because that's what you were taught, your ALO/BGO will recognize that.
So just relax. Be yourself. Be SINCERE. Be AUTHENTIC. Be CONFIDENT; (Not Arrogant). Practice your communication skills, DON'T try and practice "ANSWERS". best of luck.