Just in case anyone was interested...
1. Love your characters. Ignore the Mary-Sue litmus tests that say that if you think of your characters as anything more than pawns, you are a bad writer and deserve to be shot. If you don't care (and care deeply) about what happens to your characters, your story won't have any life to it. Readers will pick up on this, and it will make your books less appealing.
2. But just because you love your characters, don't cut them too many breaks. (This is probably what the 'Sue tests are talking about.) Treat your character as you would your child. If you stepped in to solve every one of your child's problems, that child would grow up spoilt and bratty. The same holds true for characters.
3. Don't flog a dead horse. If you aren't interested, readers won't be interested. If a story just isn't coming together, take a break. Do something else. Give up if you must.
4. Get to know your characters really, really well. It will help you keep them in character as you write, and help make them more real to the readers (who might then start fancults shipping two of your male mains. You never know). Finding out that Pat likes anchovies on her pizza, or that Sam has an obsessive need to correct punctuation on signs, might even further the plot. You never know.
5. Don't try to write immediately after reading a favourite book. Give it a couple hours to digest. Otherwise, the author's style turns up in chunks in your prose, and though it may be excellent writing in and of itself, it looks very out-of-place next to your style, whatever that is. (This one had to be learned through trial and error. Apparently, I actually don't write anything like J. M. Barrie, and trying to do it cold, without reading Peter Pan immediately beforehand, was impossible.)
6. Do the research. Any book, no matter the genre or intended audience, is always that much more engaging when it has the grounding in reality that proper details provide, and where are you going to find those details if you don't look for them? Also, glaring (or even minor) errors in the background world of your story will drag a reader out of that world faster than you can say "fourth wall". There are no excuses, especially not since the advent of Google. Do the research.
7. Make rules for your world and stick to them (unless you have a really good plot-driving reason to break them). It doesn't matter if you're on the ice moons of Appsodj:afkjwer in the Beta Centauri region, or in the court of Faerie, or on the streets of Toronto. Your world has to have rules that apply to everyone. And I do mean everyone, or you may end up with a 'Sue on your hands. (Unless you're Lewis Carroll, in which case, feel free to do whatever you like. The rest of us mere mortals, however, have to create believeable worlds, and the best way to do that it to establish rules.)
8. Learn grammar. And punctuation. And spelling. The best story, with the most memorable, lifelike characters, will go unread, unheard, and unnoticed if it's illegible. Readers won't do the work necessary to wade through a badly-punctuated, misspelled minefield no matter how good it is, and publishers will take one look at a manuscript riddled with typos and send a form rejection.
9. Write down everything that interests you. And I don't mean TV shows and bands and suchlike. That interesting headline in the newspaper, the way that guy you saw this morning in the coffee shop talked, the mysterious flash of light off the roof of the apartment building across from you, that thought you came up with at two in the morning...write it all down. You never know which spark will catch into a blaze.
10. Don't talk to your characters out loud when other people are present. (However, this is fine and even healthy when you're alone.)