One of the big problems I run into when I'm editing, and to a lesser extent when I'm simply writing with other people, is what I think of as the "how can they not see this?" issue. That moment when you're staring at a piece of work, and it is so obviously full of holes/difficulties that it's hard to believe that the author hasn't seen them. Why would they send you this thing, when surely any reasonable person could see that the whole of chapter one should be removed, that there's no plot, that the characters are flat, that they're using the kind of over the top language in dialogue that no one would ever use when speaking, or whatever else the problem is? It's hard to believe sometimes that they're serious.
And yet they are, because they really can't see this, any more than I can see what's wrong with mine. This is a lesson that I've learned at least partly through coaching fencing. There's a moment in lessons where a part of me goes 'You really can't do this move? This is easy' and I have to remind myself that it's easy for me because I've been doing it for decades. Sometimes I try to fence left handed just to remind myself of the difficulties of having to think about things. The same problem applies with writing. It's something people do for a long time, and do often quite naturally. It seems so natural that it's somehow impossible that anyone else couldn't do it the same way. But they can't, because no one has told them to, or because they don't have the practise in yet.
So what I'd like to suggest is that, if you get the opportunity today, you take a moment to tell the world something really basic and obvious about writing. Something that seems so obvious you shouldn't have to say it. You might find that there are plenty of people out there who have never heard it before.
Here's one- Even in those genres where villains are the norm, no one should normally do evil stuff for the sake of it, because real people do even bad things for reasons that seem right and sensible to them at the time. One of the best ways to achieve this is to write down your villain/opponent's argument, and try to make it convincing enough that in another world, they might potentially convince the main character. So to take a classic example or two, we have Gordon Gecko trying to convince us that 'greed is good', and the Emperor in Star Wars telling Luke that giving in to anger is the route to real power.