Cause and effect.
That's it. That's today's tip. Oh, you want me to elaborate a teeny-tiny bit? Oh, all right.
Grab a highlighter. A really bright and happy color! Now, read over your WIP and highlight the places where your MC is reacting to a story event. Now grab a different highlighter and highlight the catalyst for your character's reaction.
Oh, can't find the catalyst? Yeah. Been there. Done that.
We often need our characters to do something in order to advance the plot. But we forget to actually include the event/words/emotion that motivates them to engage in the reactive behavior. And we sorta hope our readers won't notice.
Well, our readers are sharp cookies. They will notice.
So make sure that every character action is matched with an identifiable catalyst for that action.
And that's probably the closest I will ever get to sounding like a scientist.