Neat concepts are a good base for a story and a good execution is important to drive it through. There's also the part where a good concept has no meaning without execution and even the best of writings can be hollow if the concept behind it is weak.
Physically speaking, past, present and future are simultaneously, like a giant domino effect inside a watch. Everything that happens has to have a past precursor that triggered it and an future consequences.
Naming, physically describing and giving a quirk to a character doesn't make it a character. Give it a story of its own, no matter who is it. How was its childhood, where has it been, who does it know. Nobody is an island and no one just popped into existence.
If something is supposed to be a mystery for the reader, it doesn't mean the writer can pull it out of his arse. What is more, if there's a mystery, then you have to know from heart each detail of the solution.
Don't tell your characters what to do, never. Build the character and based on it past and personality try to deduce what would it do in certain situation.
F*CKING SHOW WHAT'S GOING ON! DO NOT TELL WHAT HAPPENED!
When writing over an already existing work, canon is not a stone writing, it's a source book. It doesn't matter how close to the real thing you can write, if you can't ad anything new, then there's no point in what you're doing. On reverse, don't pretend canon doesn't exist, and if you end up in a position of contradiction, it's time to go back to the writing table.
If a famous writer you admire has an specific technique, it's because it works for that famous writer you admire. You're not that famous writer you admire, you're your own writer. Step up, figure out how to reach that famous writer you admire and f*cking do it!
Know what you're writing about. You don't need to be a consummated doctor, but if you have no idea on what happens in an operating table, you either find out how it works, or just don't go there. Same with items and concepts.
You're not perfect, because if you were, the whole damn world thing would be pointless at all. Be open to suggestions and critiques and if there's a large group of people telling you something doesn't work, you should reconsider.
However, majority and might doesn't make right. If you know -not believe, know- something works in a certain way, then to hell with everything and do your best to show it to everyone saying otherwise. A lot of people can have their opinions, but if you have a conviction worth living by, then it's worth standing up to it.
You're not God. God is a concept, not a person and you're a person. If you want to create a world, then you're responsible for it. If you create a character, you're responsible for it. Love what you create, become invested. Go down the rabbit hole and witness yourself what you have made, because it's yours and you're the only one who has to do it.
HAVE FUN! IT MAKES NO SENSE TO INVEST ALL THAT TIME AND EFFORT IF YOU'RE NOT ENJOYING IT! BE A FAN OF YOUR OWN WORK, BE A READER!