Keep in mind, I view writing like software engineering. As a result, I don't do the Hemmingway "I just sit and genius pours from my mind onto the paper" bullshit. Anyone who tells you writing is easy either has a knack for it or they're bullshitting. So, here's the things that I've learned in the 20+ years I've been in the trenches:
1) Determine your goals. I've said it before, and I'll say it again: art is all about communication. So, who are you trying to communicate with? Your flist? Genre fans? A mainstream audience? Poetry? Short stories? Long form? As a writer, you are trying to create something that will be worth your audience's time to read. And different audiences have different levels of tolerance. Genre fans, you can get away with more fantastic stuff or incorporating outside things as long as the core, the genre itself, is intact. Mainstream audiences will be quickly lost on specifics and in jokes. The journey of a thousand miles may start with a single step, but that step must be in the right direction, or all the steps in the world will never get you there.
2) Are you looking to write for fun or to be a pro? Once again, different requirements. Fun is fun. Being a pro requires more than just good grammar, spelling, and vocabulary. Don't get me wrong, those are important, but they aren't the only considerations. A pro writer is a job. You need to figure out how to channel your skill to meet the editor's need. Editors need content. They need it to be good and they need it to be timely and they need it with only minimal rewrites. Now, you can start off for fun and switch to going for pro at any time, just take the time to learn the practicalities of writing, not just the art. You'll have a better chance of success if you do.
3) Unless your goal is to become a porn writer, DO NOT DO PORN UNDER ANY CIRCUMSTANCES! I'm not talking love scenes or even explicit love scenes, I'm talking porn. As a writer, your name is your brand. People will hear your name and associate certain things with it. No matter how sexually liberated we are becoming, porn is still a black mark against you. And in the age of the Internet, it will always be lurking there, waiting for the wrong time to surface. And that goes double for women -- there is still very much a sexual double standard, and women pay through the nose for it. If someone offers you a job as a porn writer, your career is over. You are at their mercy. Everybody can write porn. There's nothing to it. That means you are replacable. If you start asking for more money, more credit, more anything that the editor doesn't feel like sharing, they'll toss you in the wood chipper and replace you with the next young person desperate for published credit who thinks writing porn is a short cut. Be smart. Consume all the porn you want, but don't produce any of it. Ev. Er.
4) If handled properly, self-inserts are your friend. To some degree, EVERY character is a self-insert. What we write is a reflection of who and what we are, what we value, and so on. For example, I like empowered women. I like women who are smart, funny, and ready to do stuff. Princesses drive me crazy. Look at the female characters I write. Holly? Rhapsody? Hannah Singer? They are all smart women, avid readers, and very much ready to take on the world. The characters reflect my biases about what I like. Since, by writing them, I am spending time with them, I want to enjoy the company I keep, even if it is ficitious. This is also why I can't do stupid characters. I hate stupid people, I hate opportunists. When they appear, like in Stress Puppy, I keep them to the background and rely on Raff and Holly's viewpoints to keep things tolerable. Raff is sort of a self-insert, the voice of reason I hope to be. Holly is sort of a self-insert, the unrepentant anarchist when reason doesn't work. Hannah Singer is sort of a self-insert, angry at a world that has twisted the concept of love into a way to control others. Any time you have a writer who does main characters with a certain mindset (Hemmingway, for example), you are dealing with self-inserts.
The trick to making a self-insert work is actually simple -- you make sure the self-insertion is not the focus of the story. A lot of people raved about Nicole Kidman in The Hours and how she deserved the Oscar. I felt it was the ultimate proof she failed. I was aware how great an acting job Kidman was doing. Ostensibly, I should not notice that, I should be reacting to the character. I was too aware that I was watching a performance. Make your self-insert a starting point, not the whole character and story. Let it go where it needs to go, not where you want it to, and you can just about get away with murder.
5) There are two aspects to writing you need to keep in mind. You have story and you have character. Some people say story is more important, others say character. Which is it? It depends on what you are doing. Stories are either the characters changing the outer world or the inner world, action or spirituality. Character is crucial for spirituality, but big events, character doesn't matter as much. If you're really skilled, you can do both at once. But that is something that not even pros can do on command, it takes just the right combination of situation and character to make both shine, so don't be discouraged if you never do. Find out what you are better at, story or character, and use your strengths in one to distract from your weaknesses with the other.
6) Writing is all about finding out what you do as a writer first. To paraphrase the Fab Five, once you establish what you can handle, you can emphasize the best, eliminate the worst, and tweak the rest. It's all about finding what you have working for you, what you can get working for you, and figuring out how to make that journey from A to B. You have to adapt. If something isn't working, either fix it so it does or get rid of it for something else that does. I regard Save Me! Lollipop! as one of the worst shoujo anime ever. It literally is every cliche in the genre you can imagine, from love interest to powers to.... Had they handled the romance differently or the quest differently or whatever, it could have been decent. But they weren't focused on whether or not it worked, just that it should have worked. Same with the Speed Racer live action movie. All the effort went into finding cool shit to put in the movie, no effort was spent finding something that made the movie compelling on its own. By way of contrast, I loved Suzuka, because I grooved to the characters more. They were likable enough that the cliches didn't bother me as much. Your likes and dislikes are where everything is going to come from. Use it to your advantage.
7) Write for ALL your characters. Wynton Marsalis famously said of jazz, "The thing about jazz is you have to listen to them. The music forces you at all times to address what other people are thinking for you to interact with them." That is what a LOT of writers, especially webcomic writers, don't get. They basically create something for one audience, themselves, and are surprised when the audience doesn't expand. You ultimately want something that, if you substituted the characters, the outcome of the story would be different. Raff and Holly in Stress Puppy -- switch them around, and the story itself changes. This means that every character, no matter how minor, has to be written. St. Michael in the Hannah Singer stories, for example. Michael is the biggest prankster in the history of Creation. So, if he's not handling business, he's doing something goofy. His dialogue and actions have to reflect this. Otherwise, he's not a character, he's a prop, a plot device that exists to move the story and nothing else. And readers will notice they are not doing things they should be doing. DC has a new heroine, Terra. She debuted in a Supergirl comic. Supergirl is at a party when a bad guy attacks, and Terra is trying to stop him. Supergirl is upset that the party is interrupted. Terra lectures her about being a hero. THIS IS BULLSHIT! When you have a newly minted character telling Supergirl how to be a hero, you're doing it wrong. Likewise, when Wonder Woman killed a man and Batman told her she was wrong to do so. (We are ignoring that Wonder Woman has, in fact, killed a couple of times.) Not only was she backed into a corner, but if anyone would understand how desperate times make people do things they normally wouldn't, it would be super-psychologist Batman. Death in the Sandman comics always struck me as insensitive for someone so alive and sympathetic. In issue #8 where she's lecturing Dreams about what he went through, she should have been understanding. She wasn't. Think about what your characters' purposes are supposed to be and make sure every detail reflects that. You have to keep ahead of the reader. If they start thinking of other ways the story can go, you'll lose them. Keep your train on the tracks.
8) Writing is jazz. It's all about flow. There will be times when you will have to break with literary conventions or proper grammar to convey what you want. Learn your basics so that you'll know when you need to chuck them aside. You want to make each word flow to the next, each sentence to the next, each paragraph, each page. You want to make something that readers start reading and when they stop, they look at the clock and say, "Where did the time go?!?" You are basically working magic to spellbind your audience. Like Rhapsody says in Sound Waves, "Flow like water. Flow like music."
Hmmm...that's all I can think of at the moment. These should be a good start to keep you from creating the next My Immortal. Don't be afraid to experiment (that's why they are called "drafts") and keep reading to see what new ideas and approaches you can come up with. You never know when you'll get an idea and something you saw will be the best way to tell the story.
Anything I missed? Anyone else want to chime in? Anyone? Bueller?