Someone on the PPW list asked for advice for a young writer. Here's what I wrote back, because I liked it, and because I'm not likely to get anything else written today:
Come to Write Brains!
Read books on writing - lots of them, but not so many that you don't read for pleasure and you don't read things you don't normally read and you don't read for research. And cereal boxes.
Submit to high school writing magazines - if there aren't any local ones (I don't know), then go statewide. They may sponsor HS writer camps - go.
Talk to your HS English teachers. At least one of them is a writer and knows good places to submit or existing writing groups (or would sponsor a new writing group). But don't believe everything they say; writers are notorious bullshitters, and teachers forget they can stop censoring kids after doing it all day long.
Put together a chapbook of whatever it is that you've written. Everything in the chapbook must be as close to perfect as you can get it! Find a buddy to draw you a cover (or do it yourself), and bind up as many copies as you can (staples are just fine), and pass them out, wherever you can get away with it.
Keep an album or fancy notebook with all your best stuff.
Live. You have to have something to write about, because plot = people, even if you're writing about alien slime molds.
Figure out why you're writing - and it isn't "to entertain," because it would be easier if you filmed yourself getting kicked in the crotch and sent it to America's Funniest Home Videos (well, it's true, isn't it?)
Carry a writer's notebook - nothing fancy. It has to be something that looks like you might be writing a grocery list or doing homework. Listen to other people's conversations, and write down what they say, just what they say, seriously, just write down what they say, just that, that's it. You can do the same thing with descriptions, etc., but it doesn't have to be a covert notebook.
Writers like to make things up. Keep this in mind during writer's groups, english classes, college, submitting work, etc. I mean, come on. I'm making this stuff up, right now.
In the end - writers write. They don't talk about what they're going to write one day, when they get the time. "Not giving up" doesn't mean "someday I'll write," it means, "Okay, yesterday, I failed to figure this out. Today, I'm probably going to fail to figure this out. Tomorrow, I'm still going to fail. I'll probably fail for the rest of my life." (You will think this.) "Eh. Here I go. Maybe it wasn't as bad as six months ago."
--At least, this is what I did in high school, except the Write Brains, because this wasn't in Colorado Springs.
Also, consider doing NaNoWriMo, if fiction's your thing. You don't have to do it in November; July is OK, especially the first time, when you don't want anyone to know if you can't get it done.