Substantive? Big picture? Line editing? Copyediting?
I recently heard some editors making the argument that the last thing the world needs is another article explaining the different levels of editing. They made some good points ... but unfortunately, since there isn't agreement on the terminology and definitions when it comes to editing, finding the right editor can be more confusing for writers than it needs to be. So even if you've read other articles on the levels of editing, in the interest of clear communication, I still need to explain my take on the editing spectrum, where I fall on that spectrum, and what you can expect from me if we end up working together—even if some of the information will be redundant.
Lack of understanding of the levels of editing can lead to misunderstandings between editor and client, but so can too much focus on the levels as separate entities and services. There's often overlap in the editing process, and while some editors have a specific, narrow focus, others do not.
On my Services page, I describe the different levels of editing I offer in order to help potential clients identify what kind of editing they need and how much it might cost ... but the truth is, many manuscripts need a unique combination of different kinds of edits—and an editor who will do what the manuscript requires, not just what a particular level of editing restricts them to. For example, a manuscript may need a basic copyedit overall, but have a few scenes that need moving or reworking because of a timeline inconsistency and a chapter that doesn't further the plot in any way—structural problems which fall under the developmental/substantive editing umbrella.
Even with a sample, editors can't anticipate all the surprises a manuscript may have in store. Would you want your editor to ignore a real problem because it isn't within the scope of the agreed-upon level and price? I suspect not. Especially since this mindset might require hiring a different editor for each level, an expense few independent authors are willing or able to take on.
The Levels
Instead of worrying overmuch about what the levels are called, you should focus on what each level accomplishes. This way you'll know what questions to ask prospective editors when trying to determine if they're a good fit. Most articles on levels of editing list at least four, and I'll break down the following levels further, but to begin with I'll keep it simple.
Building the book: Developmental Editing
Polishing the book: Copyediting
Checking the book: Proofreading
Developmental Editing
For writers of fiction, this stage is about crafting a compelling story. It focuses on big picture issues like structure, character, plot, pacing, theme, and point of view. It can be broken down into two parts:
Building the story
Remodeling an existing story
If your novel is still in the development stage—whether you have only the rough outline of an idea jotted down or you've done several drafts already—a developmental editor is what you need. Even if you think your book is complete, if your beta readers are having a lukewarm response to the story or there are things that just don't feel right but you can't figure out what they are, you're not ready to move on to copyediting and should remodel instead.
The confusion surrounding the term developmental editing stems from how it means different things in different genres. In nonfiction, especially in traditional publishing, developmental editing refers to the early stage of shaping an idea into a book (building). And substantive editing comes next: working on a completed manuscript that still needs a lot of structural changes and refining (remodeling). Freelance developmental fiction editors will often work with both stages, though sometimes the earlier stage is called book coaching.
I don't offer developmental editing because that's not what I'm drawn to or best at. I like to take a "good story well told" and make it sing, which brings us to ...
Copyediting
This stage is about smoothing and polishing. Copyediting is sometimes broken down into light, medium, and heavy (this is how it was done in my copyediting course, with a separate class for each level), but other times the term only refers to light-to-medium copyediting, with medium-to-heavy copyediting being called line editing, substantive editing, or stylistic editing.
All levels of copyediting correct for issues of mechanics and consistency; it's with language editing and content editing that the differences lie. And it's this kind of editing that gives a book professional polish, which is why I say on my Services page that copyediting corrects and line editing improves.
(All quotes from The Copyeditor's Handbook by Amy Einsohn and Marilyn Schwartz—keep in mind this is focused primarily on non-fiction)
Light Copyedit: "Correct all indisputable errors in grammar, syntax, and usage, but ignore any locution that is not an outright error. Point out paragraphs that seem egregiously wordy or convoluted, but do not revise. Ignore minor patches of wordiness, imprecise wording, and jargon ... Query factual inconsistencies."
Medium Copyedit: "Correct all errors in grammar, syntax, and usage. Point out or revise any infelicities. Point out patches that seem wordy or convoluted and supply suggested revisions ... Query any facts that seem incorrect ... Query faulty organization and gaps in logic."
Heavy Copyedit: "Correct all errors and infelicities in grammar, syntax, and usage. Rewrite any wordy or convoluted patches ... Verify and revise any facts that are incorrect ... Query or fix faulty organization and gaps in logic."
With traditionally published fiction, copyediting is usually light (whether in house or done by freelancers) since it follows other rounds of deeper editing. This has led to some confusion about the term, and independent authors who ask for copyediting are sometimes being given a light copyedit when their manuscript needs a heavy copyedit.
To help clear up the confusion, many freelancers who work with independent authors have embraced the term line editing, which is essentially the same thing as a medium to heavy copyedit. Like developmental editing, line editing is sometimes called substantive editing, which makes sense as there can definitely be some overlap between line editing/heavy editing and the remodeling aspect of developmental editing of fiction. (Note "fix faulty organization" under heavy copyedit above.)
Proofreading
Proofreading is often mistaken for copyediting. Probably because English teachers used to tell us to make sure to proofread our papers before handing them in, so we conflate proofreading with checking a manuscript for mistakes. Proofreading is checking page proofs for any errors that made it through copyediting and typesetting, one last check before going to print. Today, the definition has expanded somewhat since printing and publishing has changed, but if you haven't had any editing at all, don't hire a proofreader; it will be pretty much impossible for them to do the job. They'll either refuse the work, or end up trying to copyedit on a proofreaders pay.
So that brings us back to the original question ...
What level of editing does my manuscript need?
Once you understand the levels a little better, it should be clearer whether you need to start with developmental editing or with copyediting. In my experience, if the story is entertaining and well told and budget is an issue (as it usually is), a line edit/copyedit is the best way to go. If there are minor development issues such as unintentional point of view shifts and timeline inconsistencies, a line edit will address these (since line editing/heavy copyediting sits right where the transition occurs between developmental editing and copyediting), but you'll also get most of the nitpicky details cleaned up as well.
But if your manuscript still needs deeper work, there's no amount of polishing that can make up for a flawed story. In this case, you should consider getting a manuscript critique, which is more affordable than extensive developmental editing.
A good copyeditor will tell you if they think your manuscript isn't ready for copyediting. But if it wasn't apparent from the sample (as story issues often aren't), they may not realize this until they've already done some work on the manuscript. Both the writer and the editor will take a hit if this happens (you'll have to pay the editor for the time they've put in, and the editor may be left with a hole in their schedule and no paying work to fill it), so be aware that an editor won't do this lightly.
So do your best to determine what your book needs before approaching editors—whether through beta readers, critique partners, a manuscript evaluation, or good old-fashioned soul searching.