Every once in a while a struggling writer asks me for some advice. I don't have a ton of advice to give out and I'm especially careful about it because compared to a lot of the authors I've met I've had a very minor career as a writer. (When you've stood beside Ray Bradbury at a book signing you are bound to feel humbled.)
But here's some basic advice that I always feel confident about doling out:
Write often. My feeling is that you should write every single day. If you can't find the time to accomplish that, then write as often as you possibly can manage. But even if all you can do is jot a few notes, do it every day.
Try to sell some short stories. It's a good way to build a track record if you're aiming to become a novelist.
Don't worry about rejection. If rejection bothers you, you've no business engaging in the writing and submission process.
If you're ready to submit a novel length manuscript you'll need an agent. Search for a reputable agent, but under no circumstances should you ever pay an agent any kind of fee. An honest agent is going to earn their fee by selling your work. If they don't feel confident enough to make their livings based on a percentage of your sales, then they're probably not any good at being a literary agent.
Well, that's about it. Just a few simple things. I get a lot of questions from people who want to be writers, but those are the things that I feel should be common knowledge.