You have asked QUITE a question. This is one of the biggies that you can wrestle with for a long time, and answer in a lot of different ways. That you are asking it at all feels RIGHT to me. It’s a sign of some good thinking about your writing.
To answer this, I have to go to my standby answer to a completely different question. Many teens ask: how can I get my book published RIGHT NOW? And I advise not worrying about that, because writing a book and publishing one are two very different things. One is a wonderful act you can do at any time. The second is a business matter. And you have to get good at the first part before you can do the second. And getting good generally requires time and practice and … you said it … experience.
Because, yes, it is helpful to have gone through lots of life experiences and had time to reflect on them. It’s good to know what that feels like, and what that feels like five years later. It’s helpful to see how things tend to work in patterns. It’s helpful to see how patterns and habits can be broken.
So, say you write a book at 15. I can GUARANTEE to you that that book is going to look DIFFERENT to you at 20 and 25 and 30. Because you are going to have gone through a lot of experiences by then.
THAT BEING SAID … we have to start. We have to write something in order to write! And there are a few things I can advise. First, dig deep into your personal database of feelings. Use your imagination. Try to think of how something might feel. Try to make any possible correlation you can. Writing involves putting ourselves into other people’s places and mindsets … and they are not all places a person can really go. We can’t really go to Hogwarts, or to the disco on Mars, or 4000 years into the past. We have to IMAGINE it. We have to be EMPATHETIC.
It helps to have details. If you are writing something that takes places in the past or somewhere else in the world, you need to do a lot of research. If you are creating the world, you need to figure out the rules. The more specific things you have to play with in your imagination, the more you can feel out the space.
Reading LOTS OF BOOKS helps with all of this. Stories help you see things from many different perspectives. This is one of the many reasons writers are always saying you have to read if you want to write.
But for NaNoWriMo, give yourself a chance to give it a shot. Don’t worry about getting it exactly right on the first try. See how it turns out. You never know until you do it.