Models are known to start out oversimplified, and need lots of revision; when attempting to describe highly complex phenomena. (dotearth.blogs.nytimes.com)
I probably had about ten friends and family read it in various stages of completion (from mostly done to way - too - wordy) and did lots of revisions based on their feedback before I declared it done enough to send out to agents. (lapl.org)
It includes self - editing, getting the help of alpha / beta readers and / or critique partners, and hiring a professional editor and proofreader along with lots and lots of revision on your part. (speculationsediting.com)