I am going to use this post to demonstrate my process in creating an illustration step by step. Here you'll see the work in it's various stages throughout creation. This is a stand alone cartoon illustration, the sort of thing I would do for a freelance job or use as a sell-able print. Let's begin...
Sometimes I fill in large areas of black at this point, but it also helps conserve ink if I leave that to the coloring stage later on.
The time for the whole process from sketch to final colors varies wildly depending on the project. This one in particular took about two hours total to get to that final image. I use a MacBook computer, a Brother 11 x 18 scanner / printer combo to scan and print the paper and I use Photoshop for Mac to work with the images once they are scanned into my computer. I have a small Wacom tablet next to my laptop I use for the finer points of image manipulation in Photoshop.
Well, that's the whole thing from start to finish. Each illustration or comic I create goes through these steps to get created. Different artists have different techniques, tools and ways of accomplishing their goals all developed over time through experience. These are the steps I've found work best for me, but I'm always on the lookout to improve the way I do things.