Reviewing with River

All of them actually.

If you are not writing, then review. Not having enough time is something that has slowed down my reviewing process, but whenever I do, it refreshes my mind.

It helps me go deep into the world that the author had created and then look around.
Then if I find something worthy of mentioning, I certainly let him know.
But structured review is something on a totally different level. It not only helps the author to get a clear picture of what the reviewer has to say, it also helps the reviewer to express properly.
Any such review needs full concentration and that's where you find yourself trying to improve.
So if you are reviewing, regularly, you'll see that you have taken yourself to another height of writing which is much better than what you have been.