Read a lot. A LOT. Write. Do not apologize if you suspect the writing is bad; it willl only improve if you keep doing it.
Be aware that writing pays poorly and erratically and that you will probably never get to quit the day job.
Join a critique group. Listen to them but do not take their every word as gospel, because it's your story.
Learn, for the love of god, the rules of grammar and how to spell. You can break them later, but know what you're doing first.
If you genuinely want to make a career of writing, you have to be pretty obsessed. You have to want to write *more* than you want to go to the movies/hang out with friends/spend time with family/etc (at least most of the time). Writing as a career is generally something that is worked in around another job, so if you want it, you have to find/make the time. A writer friend of mine says if you have time to watch TV, you have time to write. She's right.