Students find it easy(wrongfully so) to delete from their drafts, and their proclivity is to just hack away. It's important they understand how and why we delete from our drafts, so I believe some direct instruction is necessary here.
The following Deleting PowerPoint was created by using the Purdue OWL page, where I found passages with excessive words. It shows examples of sentences that can use deleting as a strategy for revision. The last passage has several different possibilities, and having students talk at their tables proved really beneficial for their understanding. It was cute to hear little debates like, "No, you can't delete that word; it's really important!" I really tried not to step in, and instead reminded them to read the passage without the words in it to ensure clarity of meaning.
When we were finished with the PowerPoint, I gave students time to work on their Revision Strategy: Deleting activity from the book. Those who could prove mastery of the concept were released to work on their own drafts by using the deleting strategy.