So...you want to be a writer.
Wouldn't it be easier to get a job in banking or health care? Get the good salary with benefits and a solid retirement plan? Work with other like-minded people? Pay your bills on time? Making a living as a writer is hard. I spent fifteen years at it—full time—before I finally had a year in which I earned as much as the average union laborer at a Ford plant, and the only reason that happened was because I got lucky and won a National Book Award. You know what the odds are that you'll win an NBA? Trust me, they bite.
Still want to write? I don't blame you! Writing is the finest and most important and most rewarding of all vocations—except for the part where you have to buy food. So by all means, stock up on Ramen noodles and write on. But don't say I didn't warn you.
Here are a few tips. Good luck!
1. Keep your eyes and ears open. Watch how people talk and move. Listen to what they say. Good writers develop wicked observation skills.
2. Think about why people do the things they do. When somebody does something that doesn't seem to make sense, try to understand why they might have done it. When you hear of someone doing something you could never imagine yourself doing—something wonderful and courageous, or something evil and depraved—imagine yourself doing it. Imagine yourself being that person, making the decision to perform that act.
3. If you are not sitting with a writing instrument at hand, you are unlikely to be writing.
4. Read voraciously. Read books about things you think you aren't interested in. Read books about nematodes, and sawdust.
5. When you read a book you like, read it again. Try to figure out what makes it good. The better the book, the more difficult this is. Sometimes it takes three or four readings to get to the bones. You might have to re-read a book until you hate it to find out why you liked it so much the first time.
6. Start writing with a question. Write toward an answer. If you reach the answer too easily, rephrase your question.
7. Read, rewrite, set it aside, reread what you wrote, throw a bunch of it away and revise the rest. Repeat as needed.
8. When you get stuck, go do something that is not writing. Make yourself a peanut butter sandwich, or walk the length of the Mississippi.
9. When someone slams your writing, listen carefully to what they say. Then tell yourself that he or she is a tasteless, moronic, jealous, mean-spirited, ignorant jerk. Then go back to your garret and figure out what you did wrong.
10. Why do these lists always have ten items? If humans had evolved with four digits on each limb, would our lists be shorter? Or, if we used our toes more, would David Letterman be reading a "Top 20" list? Okay, one more: Never, never forget that writing is not just an act of expression, it is also an act of communication.
For some writing tips that are a bit more concrete and, perhaps, useful, go to James Alan Gardner's website. Gardner is one of the best SF writers working today, and his "Seminar on Writing Prose" is one of the most clear-eyed discussions of the art and craft of writing that I have seen. Check it out. And read his books, too.
I also recommend Stephen King's book, On Writing.