I'm to the point of wanting to start diving into specific artists, but before doing that, realized it would be best to nail down the process behind things first. Talking in detail about how great an inker is doesn't do much good if the reader doesn't have a knowledge of inker that extends beyond 'tracer'.
That means this post is dedicated to breaking down the different types of things that go into making comics. Now, the focus here is on American comics, as the techniques and some roles don't exist in other types of comics around the world. And even then, this is generalized. Not all comics use all of these roles. Some are painted, some aren't inked, some are silent and lettering isn't necessary, etc. You get the point.
Attached we have examples of various stages (script, inks, and colors) to help show how things change and look at various stages. These are from a book from Marvel a few years back: Immortal Iron Fist #1. It was written by both Ed Brubaker and Matt Fraction, and the pencils and inks were handled by David Aja, with Matt Hollingsworth on the colors. I apologize for not having the pencils to compare but Aja handled both the pencils and inks, and my best efforts to find the pencils have failed. Still, this should give a good visual idea of how things work, especially from the script to art stage. And I highly, HIGHLY recommend clicking the thumbnails to get a better look at the images. The thumbnails really don't do Aja's art any justice.
So I'll start at the 'usual' beginning.
Writer: A writer does about what you'd expect in comics. They write. Shocking, I know. What's worth mentioning here is the how, as it can vary from writer to writer. There is no standard form of a comic script. These days, it isn't uncommon for a writer to use a screenplay style very similar to movies and television scripts, but it is in no way universal. Many writers break things down as simply as a basic panel description of what they want the artist to draw, and a few lines of dialogue, with little else. Some, like Alan Moore, can writer pages on how the mood and feel of a single panel on a page should be.
It really comes down to how the writer and artist work together. Some artists love a stricter breakdown, while some love the freedom of just being told "They fight, have fun" in a script. This is taken to the extreme in what is called "Marvel Style", called as such because of how common it was during some of the earlier days of Marvel thanks to Stan Lee. With this style, the writer just gives the artist a basic plot outline for the entire issue, with no real breakdowns, and then the artist sends back pages and pages. With that, the writer THEN puts in the dialogue. With Marvel Style stories, the artist is much more intimately involved in the writer process, and it's something that some people swear by.
Layout Artist: This is one of those roles that is many times wrapped under the label of penciler. But there are some artists that simply take the script and do breakdowns, or layouts. Sometimes it's to save time for the penciler, sometimes not. Some pencil artists like to have another hand to help them break down panel shapes and the overall way a page flows.
Pencil Artist: Here's the artist that usually gets the most attention. This is the person putting down the final, well worked pencils that determine pretty much everything. All the art on the page is based off of what happens here. If there is no layout artist, this is the artist who truly sets the flow for the page. A good pencil artist is essential to a readable book.
Where the writer sets down the words and the idea, it's the pencil artist that sets it all into motion. In some terms, they could be seen as the director of the movie, putting their vision onto the page from the framework of the script. But there is more to it: The penciler is also all the actors, the set designer, and everything else. This is a stage that can truly make or break a book in how you relate to the characters, or simply if you can read the panels in the correct order.
Storytelling ability is king here even more than rendering the art perfectly.
Inker: This is not the 'tracer' as some would say. In every single way, that is a failing to understand what an inker actually brings to a comic. Years ago, inkers were credited as an Embellisher, and that's still a very good way to look at this step. An inker takes the pencils and renders them in solid blacks and whites, sometimes with tones of grey depending on the medium they've chosen to use.
The importance of the inker is in bringing to life and shaping the forms the pencil artist has already put down. Solid, strong blacks are a staple of American comics, and balancing those on a page is a subtle and essential art. In many ways, this can be seen as a type of extremely nuanced and very important shading on every aspect of the art.
Colorist: Here is another more self-explanatory person in the making of a comic. The colorist, obviously, colors. But this goes further than simply keeping in the lines and making things pretty. All the fundamentals of color theory apply here and are vital to making or breaking the overall work.
The inker has already given a strong pass of blacks and whites, which can help to determine where the shadows are, but a good colorist can make them even better. Color pallets make or break a story, just like they do for any other work of art. Sometimes a flat coloring style is used that resembles the older, four-color process that we're used to seeing in the comics from the 60s and 70s, but other times the art is fully painted: be that digitally or traditionally.
Letterer: And now, with all the art down and, hopefully, finished, another important person in the process comes in. The letterer adds nearly all the text. Word balloons, captions, title pages, etc. All of that is for the letterer to do, as are many sound effects that aren't necessary integrated into the art by the pencil artist.
While all of this is, obviously, important, the letterer does something else that is more subtle but is arguably one of the most important parts of a comic book. In placing word balloons and captions, the letterer will show the reader how to read the book. A good letterer will bring your eyes along the image that the pencil artist has already set up, from one piece of text to the image to another. This can go in traditional, left to right manner, or, if done with skill, back and forth in nearly random patterns that follow the art.
Everyone Else: And that is in NO WAY the entirety of people needed to make a comic, but those are who we're focusing on. Beyond them? You've got editors holding the communication lines between them all and making sure the book actually comes together, assistant editors trying to keep whatever they're assigned to straight, cover artist (usually a different artist than those working on the interiors of a book), graphic designers to help with everything from logos to organizing cover designs, to the interns helping wherever they're ordered to and hoping to one day turn the internship into a job. And even THAT isn't everyone, but you get the picture.
Comics come about due to the effort of a great many people. Sometimes. Other times? One person does it all. Sometimes there are only two. But one way or another, most of these things tend to be necessary for a comic to happen. Sometimes the same person does multiple parts of the process, as we see here with David Aja penciling and inking the work. Okay, we don't see the pencils, but you get the idea.
Once I get to talking about specific artists, we shall see if this very brief overview has done any good.