Have you ever been really, really, really hungry? Have you ever stayed awake for 48 hours in a row? Did you break a bone? Did you fall in love...or fall out of it? Well, why don't you write it?
When you're a writer, you're going to hear the phrase life experience a lot. But you don't have to go to Italy or kill a guy in order to get life experience. Everything you've ever been through, no matter how seemingly mundane it is, can help you write a book. If you've felt hunger, if you've worked out until your muscles ached, if you've smelled the perfumed scent of a cigar -- all of it, any of it, can lend rich details to your book. And the other stuff that you haven't done? Well...you can use research for that.
Even if you feel like you haven't experienced much, you have experienced some things. You've gone to school. You've dressed yourself. You've taken a bath. If you can write about these things, and write about them well, you can make your book that much richer. Use the life experiences you'v got as the foundation for your scenes, and weave the plot on top of them.
What do I mean by that? For example, your character has been asked to Homecoming by two guys, and now she has to ponder this decision. Why not have her think about it while taking a shower, or a bubble bath, or whatever you like to do? You need two characters to talk to each other, so why not put them in a pizza parlor because you always hang out in a pizza parlor? You're uniquely qualified to write about these things because you've lived them, so you can add important details that make these scenes come to life.
Even the smallest experiences can be integrated into your book, and should. It's the small details that make your book feel more real and much more rich. Use all of your life experience to make your stories more complete and give scenes a strong sense of reality, and you'll notice the difference in your writing.