Action scenes

I'm sure you've read both types of books; the books where they sit around talking and nothing ever happens, and the books where there are so many fight scenes it makes you exhausted. In my opinion, there are healthy middle grounds.

Fight scenes should be used to emphasise moments and to move the plot forward. Such as, when our hero escapes from the prison. That's a big moment in the story, and it'll be underlined by the brawling he does to get out.

Also, a lot depends on the genre. If you're doing fantasy, big epic battles aren't mandatory, but they sure don't hurt. In sci-fi, there's a sense of danger, that there are fantastic and wonderous creatures out there and most of them want to kill you. In sci-fi, wars are not neccesary, but make sure the world feels somewhat dangerous.

In mystery, you can very easily go the whole story without any action encounters. But if you're working with something like a murder mystery, it's not so far-fetched that a shoot-out may ensue.

In children's books, go for lots of gore. Guns are A-OK, and make the victims scream "IF ONLY I HAD EATEN MY VEGETABLES!" You'll be a role model.