See? you do need to be more confident!
You said you've never really accomplished anything- yet here you are- a top scorer in a writing test- practically a master of the English language! and a published/publiclly exhibited artist! Be PROUD of your achievements.
If you are going to write a resume, and I think you should if you have time, do a goggle search on resume writing for young adults or kids (sorry, I know your not a kid, but us old timers will always call you that, even when you're 40) for help on how to list your life experience, jobs, (even chores) talents and skills. As someone else mentioned- this has to be accurate information, don't claim to be able to do something you can't and don't claim to have experience you don't - but you if you look at all your little achievements and experiences - and what personality traits they highlight- you'll be suprised what you can put down honestly. Creativity and an artistic eye- that was publicly recognized- good written language skills, the reliability to care for pets that require a daily commitment- it will likely sound much better than you're thinking right now. Brainstorm what you do or have done, and what personality trait it highlights, then pick the best for your resume.
A resume should only be one page. Format it with double spacing, indented bullet points. Your name and contact information up top in big letters (no funky fonts or graphics please) a description of your "career objective" and you're half way there.
A nice list of references at the bottom (not your mom- but if you have teachers or guidance counselors or neighbors who's fish you feed while they're on vacation- stuff like that) and you're most of the way there. When it comes to references, List their names, phone number and brief description of their job title, not how you know them. Don't put down Mrs. Smith who's dog I walk. Put down Mrs. Smith, director of XYZ at so and so company. Make sure anyone you put down as a reference knows you are using them just in case they call. (no one ever does, but just in case)
It wont take much to fill up the middle. All you are proving with the resume is that you are willing to make the extra effort, you are professional, have a decent command of the language and have respectable people who will vouch for you.
One of the most impressive resume's i've ever seen had almost no job experience listed- but it was brilliant.
Also- try practicing the interview alone. Think about the questions and answers you might give- then say them outloud- and here's the hard part- say them WITHOUT :
Ya know
like
Uhh and um.
Practice tonight- think of a question and start to answer it outloud with a pen and blank piece of paper in hand. get all the way through to the end, and everytime you Ummm "like" or "ya know" make a mark on that paper. You will be shocked. Bite on your lips if you have to, but to sound like an mature adult, you have to leave those behind.
Your thoughts in your head and what comes out of your mouth can be vastly different! practice and it will help you not just in this interview, but in all kinds of relationships througout your life. Communicating is a skill that you have to practice to get good at.