One big problem I've had turned out to be really easy to solve.
I'm sure most/all of us do it. You write some, then go back and make a few tweaks. Adding, removing, replacing, and rephrasing words and sentences.
You reread the final version and it looks good. You read it out loud to yourself. Happy with the result, you move on.
Later on you glance at the story again, and see your mistake. "Betty grinned as as she..." How did you miss it?
Our brains sometimes outsmart us. It's like our mind preforms it's own autocorrect.
In my case, I fixed this problem by using text-to-speech. Closing my eyes and listening to a computer read back exactly that I typed in has been invaluable. This removed an entire class of mistakes from my writing.
There are many out there. I like amazon Polly because it's free for something like 5 million characters month, and has many hight quality voices to choose from.
If this is already common knowledge, sorry... :)