A good story needs a good plot, and good characters. If the plot is lacking or cheesy, or if the characters are too perfect or too flawed, then the whole story falls flat. There is an art to storywriting, and here's some advice on how to perfect it. I will be using the characters from We Are Gods - Jason, Lucy, Rik, Sean, Charlotte and Scott - to help me.
As I'm sure you would have been told in primary school, the plot of a story follows an arc: Introduction, Build-Up, Climax, Resolution and Conclusion. Generally the introduction is short so as to get on with the story; the build-up has a few minor problems that are relatively easily solved by the main character, and is therefore definitely not a minefield; the climax is the true danger, the true problem, that is significantly bigger and more difficult to solve otherwise it might just as well be part of a build-up; and the conclusion is in the last chapter at most.
Before you do anything I would suggest making a few notes for each part of the story. They don't need to be extensive, just short, sharp, easily-memorable notes that get the job done. Like so:
Introduction: Jason's average day, goes to cafe
Build-Up: Jason smells burning, thinks it's coffee. Thinks nothing of it. Smoke from kitchen.
Climax: Fire spreads to behind counter. Waitress staggers out from the kitchen. Jason tells everyone to evacuate.
Resolution: Firemen come and extinguish fire.
This is the part where you can have the most fun. You get to design your own characters, perhaps fashioning them in your image, or making entirely separate, entirely unique appearances and personalities each time. Remember to not make them Gary and Mary Sues - utterly perfect, no flaws whatsoever - and don't make them so flawed that their very existence is torture. My golden rule for characters is to have 1 to 3 flaws. Here is the information for Sean:
Name: Sean William McLoughlin
Age: 18
Appearance: Dark hair of unknown description, as he never takes his jeff cap off; warm brown eyes; 6' 4''; semi-muscular
Personality: Cripplingly shy, cowardly, but otherwise friendly; very hard-working. Exceptional listener, which is why he's such good friends with Lucy.
You can also give your character a quirk - a trait that is neither good nor bad. Here I've had Sean 'never take his jeff cap off', and later in my book I explain why not, and most of the time you will have to as well. It can also be just one of those things your character does or does not do that can't really be explained, and doesn't really need an explanation anyway.
You can also redeem your character of a bad characteristic later on. This is called character development, and if you have none then your characters become quite monotonous and not that believable. Here Sean is 'cowardly', so later on I redeem him of this by having him being extremely courageous in the face of the death of his friends. They are falling down a huge canyon and Sean is left on his own above it as he was the last in line and so saw the canyon form earlier than the others. This is my favourite part of the book, so I'll give you a nice big chunk of it.
"No!" Sean screamed, scrambling to get hold of Lucy's hand, but she and the others disappeared into the dark depths. Sean knelt down at the edge and hid his face in his hands, tears dripping through his fingers.
"Don't go..." he sobbed quietly.
What use is there in crying about it? demanded a voice in his head. Go on, tell me.
"I - bu - I - I don't know."
Chin up, lad. If you don't do anything soon, all of your friends will die. Your brother. Your sister. Everyone you love will be gone if you don't get a grip and do something about it.
"But... what is there to do?"
Jump.
"Are you mad? You know I hate heights!"
You're just going to have to trust me on this. Can't even trust your own subconscious? Go on, jump. I promise you'll be safe.
Sean looked down at the blackness of the canyon, then nodded to nobody in particular. He was to save them, somehow, and he was going to be brave about it. No more crying, no more hiding away, no more weakness. He walked away from the edge, breathing slowly and deeply, steadying himself for the big event.
He took off his jeff cap and laid it carefully down on the ground.
He turned back to face the hole, then sprinted towards it at full pelt. He dolphin-dived, feeling the wind rush past his face. He was doing it. He was saving them, he was being brave.
... Now what?
The short sentences and paragraphs at the end of the passage create tension and significance as he has never actually taken off his cap before, implying that he would do something he never did before to save his friends, but now that he is in there, how's he going to get back out? Similar tension can be created using long sentences broken with multiple commas, like the sentence prior to this one.
Self-insertion is, in the simplest terms, the author putting himself into his own story. This is all well and good, but it has to be done correctly. If you are essentially a deus ex machina (God of Machine, i.e. Solver of All Problems or SAP) it is an instant turn-off for readers, because you ruin the conflict. By all means be helpful but for goodness' sake do not make yourself out to be a SAP.
The way to self-insert correctly is to be yourself. If you are unsocial (not getting on well with others, as opposed to 'antisocial', which is actively going against society), don't suddenly make yourself a social god for the sake of advancement of plot. If being yourself presents new obstacles, great! That's what readers want in a story! However, if you find that you have hit an obstacle too big to solve, perhaps try and redeem yourself earlier, but again, not too much. I'm pretty sure your name isn't Gary or Mary Sue. If it is, then don't try to be absolutely flawless. Nobody is and nobody ever will be.
Now for the bits that really drive the story. I for one am fascinated with fantasy, so I like to use magic and alchemy most often. For action I suggest having communication devices like spy watches, and for romance perhaps try phones, a cafe, things like that. They have to be objects or places that really tie the characters together and present their own mini-problems; maybe the cafe your hero has asked your heroine to meet him at is too far away, or too uncomfortable, or clashes with her perhaps higher standards.
As an example I will give you a much earlier excerpt from We Are Gods, where Lucy demonstrates her magic for the first time in front of Jason and his brother Sam. Jason is being attacked by a crowd of people due to a mishap with his magic, and Sam can't help, because he has none.
Sam watched helplessly as Lucy became another target, but she didn’t seem the least bit phased by the blows they sent her way. In fact, she didn’t move at all until she’d thoroughly had enough of such rudeness.
“ENOUGH!” she roared, flinging her arms wide, sending a pulse of pure white energy exploding outwards from her body, sending the crowd flying backwards and tumbling over each other, tripping over furniture and falling over. It was quite the spectacle. Jason was unaffected though in a little shock from the sudden outburst.
Lucy is normally a calm, composed teenager with an incredible mind, but clearly the crowd has gone too far in their efforts to fix whatever Jason did (I'm saying nothing). It has also been implied that she is trained in her magic and in defence, otherwise she would be on the floor crying within one minute.
Now that you've made your notes on the plot, made your character(s), and thought of the extra bits, it's time to flesh it out. Don't be tempted to describe everything from the tiniest dew drop to the largest oak tree - that's called purple prose. An example of purple prose is:
The steel streetlight flickered sleepily as the tall oak tree with brown bark and green leaves rustled in the cool breeze of the black night. Grey squirrels and orange foxes danced the dangerous tango of the extensive food chain on the green, dew-dropped lawns of the sleepy Close.
We know streetlights are made of metal. We know oak trees are tall, and that the bark is brown and the leaves are green. We know all of that. So why tell us? Just describe what they're doing and only occasionally describe what they look like if their colours or appearance can vary. An improvement on the purple prose passage:
The streetlight flickered sleepily as the oak trees of the Close rustled in the cool breeze of the night, which had gone from a beautiful magenta only an hour ago to utter black. Squirrels and foxes danced the dangerous tango of the food chain on the dew-dropped lawns in front of dampened houses.
Much better.
Here we can infer that it's most definitely night-time in midwinter (the only time when the sky goes from 'magenta' to 'black' in an hour), and that it's been raining, or still is. The squirrels are being chased by the foxes in such a weaving way that it looks like some sort of dance, and at the end of it the squirrel will be eaten.