People ask me what I do when I edit or proofread, so this seems to be a good place to tell them.
I do the obvious: I look for typos, misspellings and factual errors. But it goes far beyond that.
While editing and vetting a novel last year, I quickly realized that the author had an Army general using a rifle to kill snipers. I told her that it was her business, but a general would never be put in that situation. A colonel? Maybe, but not likely. A major? Possibly.
She laughed. It turns out that she knew that a general would never be caught with a rifle shooting snipers. She hoped that no one would catch it. If I caught it, she said, someone else would; so she turned the general into a major. The storyline immediately became more believable.
One of her characters was a double agent, and she'd use one name part of the time and the other name at other times. I found it confusing, and I told her so. I also reminded her to occasionally add that Joe is a colleague and Jim is a relative; in fact, it wouldn't hurt to give the full name, Joe Martin and Jim Bronson, or whatever the names are. In a 300-page novel, the reader needs help in remembering characters.
In another book, this one about ancient Egypt, she had a character whose name didn't seem to fit the time and place. She changed it.
Most of my work is grunt work, whether it's in fiction or non-fiction books, letters, web sites, term papers or whatever. I look for parallel construction, changes of tense, tangled sentences. If I find a 50-word sentence, I'll look for ways to convert it to a least two and preferably three or more sentences.
I look for the quickest and simplest way to say something.
I ask questions: Does the writer need "utilize" when "use" will do? Can we say this in 50 or 100 fewer words? Is this sentence clear? Can we make it crystal clear?
Is this comma necessary? Should it be a semicolon or a dash? On further review, would this sentence be better with a comma? Is the writer using too many exclamation and question marks?
The author mentioned above had trouble with punctuation. She'd have a quote with a question or exclamation mark AND a comma -- "We never eat out anymore. Why is that?," Martha asked. She didn't need the comma.
I've been pleased with her improvement. I find fewer typos and outright mistakes. Her copy's cleaner and easier to read.
Recently, I've been "Americanizing" British non-fiction books for sale in the Americas. I change "favour" to "favor," "maximise" to "maximize," and "behaviour" to "behavior." "Loo" becomes "toilet"; "solicitor" turns into "lawyer", and "lift" becomes "elevator." With the help of Google, British slang is translated, and when I can, I change soccer analogies to baseball, basketball and American football. It works better for U.S. audiences.
I do more than that, of course, but you get a flavour, no, flavor of what I do.
I remind the writer to proofread and edit his/her work a few minutes and a few days later, time permitting. I tell writers to always get a second or third pair of eyes on your work, and don't trust Aunt Jane or Uncle Bernie. A professional editor can make your writing sparkle and make you look good.
To be honest, I think my job is simply to help the writer and the reader. Like an offensive lineman in football, if I do my job correctly, you won't even notice that I've been there.