As an editor, I want to help writers grow in their craft. I believe each author has a voice and style all their own, and it's not my job to change that. It's my job to help bring out the best of that voice and style.
I edit in Microsoft Word, and I use the Track Changes feature, so that my changes can be easily viewed. I leave comments as I go to explain why I corrected something, if I was confused about a specific point, or to point out bits I especially enjoyed.
Once I am done editing the manuscript, I'll send it back to the author, and I'll ask that they leave the Track Changes on while they're working on what I sent. It is helpful if the author accepts any editing changes made. If they disagree with something I edited, then they can leave a note in the Track Changes, or they can send me an email so we can discuss it.
After the author has finished going through my edits and making any additional changes, they will email it back to me. I'll be able to see all the changes they made in Track Changes. We can do final corrections, I'll remove all the Track Changes marks and notes, then send the clean version back to the author.
It typically takes about four weeks for me to do the initial edit on a manuscript, and maybe a day or two to go over the changes once the author sends it back to me. Occasionally, if the book is shorter and in quite good shape, it might take two weeks, but expect at least four, perhaps longer if the book is very long or requires a lot of work.
Please note that I primarily edit fiction books, but I will also edit non-fiction, and while I will consider pretty much anything, I prefer not to edit heavy erotica or occult stories.