I recently had a discussion with several fellow editors about voice and style. Namely, when to leave it in and when to take it out. Every piece of writing has a natural voice to it. As an editor sometimes I have to make a decision about when to leave something that's not wrong, but could be written clearer, and when to rework a sentence from the ground up. Good editing is like good tailoring; the original might fit without falling down around its wearer's ankles, but with a nip and a tuck, it suddenly looks sharper–it just fits right.
Understanding an Author's Style
The first thing I do when working on a new writer's pieces is read the piece all the way through. This is important to ensure I understand that person's unique style and that I don't accidentally cut something they refer to later on. I also frequently print out the piece so that I can circle and underline areas I feel are important. I jot notes down in the margins and draw arrows between sections that are on similar topics.
Only after I've done all of that do I begin to change things.
Pass Two: Proofreading
On my second pass through a piece I look at word choice and check for common grammatical mistakes. I make sure the writer has used the right to, too or two and their, there or they're. I double check the spelling of any advanced vocabulary.
I also notate any sections that read less smoothly than others. A good way to pick out awkward phrases is to read the entire piece out loud; when I'm home alone, I do precisely that. If I'm working and there are other people around, I read silently but mouth the words.
Once I know which sentences need a bit of work, I'll begin the real work: cutting and re-sewing pieces together for that perfect fit.
Creating Seamless Copy
After a good editor has worked on a piece often even the writer can't tell exactly what was changed; they know it reads cleaner and that the words fit their meaning just a little more snugly, but without comparing it to the original it's hard to pinpoint precisely where a word was swapped out or comma removed.