When you finally sit down to write, there are some things you should keep in mind.
1) If your character in any way resembles the Anakin Skywalker character from the last two Prequil Star Wars movies, throw it away and start over.
2) Don't be afraid to use humor! The most successful books are at some point funny. Or they have a warm and realistic romance. Usually both. Why do people in the Science Fiction genre think that Sci Fi is incompatible with 1) humor and 2) religion? Honestly, people… throwing out those two things makes a story absolutely NO FUN, which is why Sci Fi has become the most unpopular genre out there.
3) Here is a general writing tip: AVOID IMMORALITY. Most of humanity from any culture hates lying, cheating, adultery, backstabbing, stealing, faithlessness, betrayal, sleeping around, and other such smut. If your so-called “Hero” engages in these activities regularly, I would seriously reconsider his position... and maybe make him into the BAD GUY of the story. Trust me on this one. You will alienate your reader if you are constantly letting your Hero get away with all kinds of disgusting behavior that in real life nobody can—or should—get away with.
And if you do allow your Hero to engage in this kind of behavior, make sure he has to deal with the consequences of his actions. This isn't just a preachy morality tip, this is reality. People only get away with this kind of destructive behavior for a short period of time: eventually they will hit the wall. Because in a book the plot must be wrapped up in a short period of time, that means the consequences of these kind of antisocial behaviors have to be addressed somewhere before the last page.
4) Don't be afraid to follow your story to the logical conclusion. Most authors become afraid and put on the brakes because they are afraid 1) their bad-guy will be killed, or 2) their main character will become a powerful leader. In short, the balance of power will permanently change, and their world will stop having conflict. Thus, no more future stories. DON'T have your Hero take over the kingdom in the end, only to give it up in the end and wander off to be a humble wanderer! That is LAME! We'd rather read Book Three with Hero being the harried and overworked leader of a small nation than a wandering loser. LET THEM ACHIEVE THEIR DESTINY.
Don't worry, Fantasy has the most flexibility as far as your reader believing you. Science Fiction has less, and Mystery has none. But don't abuse the credulosity of Fantasy readers, it gets annoying after a while. You can only break one or two rules.
5) Be happy when you get your character into a situation that looks like he is done for. Yeeey! You have finally reached a point in your plot where real thrilling action could happen! Here is your goal: ALL you need to worry about is somehow finding a way to keep your Hero breathing; he can lose EVERYTHING else. Yes, blow up his spaceship! Let him somehow manage to get into an escape pod just as it goes up like an atomic bomb! Now you have a great situation where your Hero has to fight up from the bottom as the Underdog, and his success at the end will be fantastic! Remember kiddos: never pass up an opportunity to mash your Hero. If your Good Guys never lose anything, you will bore your readers into book burning.
6) The essence to great writing is flashes of inspiration... what the ancients called “the muse.” I won’t go into what the Muse is, but I will emphasize here that the more pure raw inspiration (lightning-like flashes of brilliant illumination that hit you) you put into your story, the better it will be. EXPECT this inspiration, and by all means, DON’T listen to anyone who says inspiration is rare or hard to find! The fact is that inspiration is only as rare as you believe it is. If you believe you are brilliant, you will be (and believe me, anyone can be brilliant; genius is simply like being a bodybuilder: you exercise your brain enough and it will grow strong!)
You can be brilliant, and you can have a never-ending flow of inspiration into your stories if you just make a conscious, determined decision to have it. You won’t see a million downloads of raw inspiration a day at first, it will start with a little trickle, but never start believing you are dumb or dried up. I don’t bellieve in the mythical “Writer’s Block,” and I have never had it... except once, when I became afraid I might get it! (But I soon realized I was being stupid, and stopped believing in it, and it went away.)
Remember, the only thing you have to fear is fear itself.