All you have to do is...
Don’t just be technical, make it beautiful. Make sure your writing flows with ease, varying your sentence length, make metaphors, use symbolism, etc…
But don’t overdo it, don’t be cliché. Be unique. Stick to the genre you chose, but be surprising within it.
Have a unique and special setting, but make sure your world makes sense. Stay away from things that have already been done.
Make sure your character is realistic and well developed. Don’t make them too beautiful or too perfect, everyone needs relatable flaws, but make sure they’re still likeable. While making them relatable, make sure they’re also unique.
Now fill out their relationships with other characters, who better be just as developed as they are. Well, make sure you develop them, but don’t spend too much time with them or people might get confused. Don’t have too many or too few supporting characters either.
In dialogue, make sure everyone speaks with different voices, don’t let two characters sound the same.
Give your characters good names. Don’t let them all be similar—remember, you didn’t name all of your characters, their parents named them.
Make sure the characters are realistic. It’s easy to write everyone or most people as beautiful, but everyone has flaws, and a realistic world takes all kinds.
Know your character in depth. To do so, you’ll probably write a detailed backstory for them. Then you’ll have to decide how much to reveal, when, and how. Avoid info dumps.
Avoid info dumps in world building too. Even if you have a complicated fantasy land, make sure you don’t slow down your plot with pages of description. Tell—I mean show—just enough.
Make sure your romance is adorable and sweet but not at all cheesy or cliché.
Have the perfect villain, and make sure everything he does makes perfect sense from his perspective, despite coming off evil and heartless to others. Humanize him just enough.
Describe your characters, and do so beautifully, but don’t over or under do it. Don’t use easy-outs like putting your character in front of a mirror or have them look at pictures of themselves.
Give your story exciting twists and turns. Make it unpredictable (but realistically so, don’t jump outside your genre). Give plenty of conflict and suspense, and don’t resolve things until the perfect moment, in the perfect way.
Make sure your writing flows throughout scenes, and from one scene to the next. You can decide how much time passes and how quickly, but make sure it all makes sense and doesn’t feel choppy, and transitions aren’t too sudden. Also, make sure no scenes drag on.
Know your genre and make sure your content is appropriate for it, for example, no graphic sex scenes for a YA novel.
Do your research if your writing about a subject you’re not an expert on. Spend plenty of time reading and asking questions. Also, look up writing tips online, but don’t spend too much time doing so. Many writing tips are contradictory as well, for example, lists of alternative words for “said,” when “said” is actually just fine.
Think of the perfect title for your book. It should be simple, but unique and catchy. Look up your ideas to make sure you’re coming up with something new.
People do judge a book by it’s cover, so get yourself a beautiful cover.
Develop your own voice and style as a writer. Sure, you can be inspired by others, but you don’t really want to sound like anyone else.
End your book in the perfect way—although, “the perfect ending” is debatable. Actually, all of this is debatable, and no matter how you write, some people are still going to hate your book. Others will still love it. But I think the only thing we can all agree on is that writing a book is in no way at all “easy.”