In the paper, ‘Writing Tips for Ph.D Students,’ by John H. Cochrane, we can find this conclusion,
"May economists falsely think of themselves as scientists who just "write up" research. We are not; we are primarily writers. Economics and finance papers are essays. Most good economists spend at least 50% of the time they put into any project on writing. For me, it’s more like 80%.
Pay attention to the writing in papers you read, and notice the style adopted by authors you admire.
I got a lot out of readingWilliam Zinsser’s On Writing Well, and D.McCloskey’s Rhetoric of Economics. I also found Glenn Ellison’s "The slowdown of the economics publishing process" in the JPE useful for thinking about how papers should be structured (and refereed and edited, but that’s another story)."
50:50 is big ratio. We really need practice. You know, his advices are all helpful to refer and you will find it easily.