I thought I'd go a little more in depth with my comic book process, as there are a few stages before I even get to the final thumbnails. I can't say I'd recommend doing it this way because it's really a lot of extra work, but it's what I'm comfortable with.
For the example I'm using a 5 page Rex Steele comic that was done for "Digital Webbing Presents" #29
The very first step in the process was discussing the story with my partner Matt Peters. Once we figured out what we wanted, I drew a series of thumbnail storyboards of the entire story (as you see below). I'm a storyboard artist by profession so this is really the most natural first step for me. This also allows me to get a panel count, and therefore a page count. Our goal in this case was to make a 5 page comic, and as you can see I had way too many panels to do that.
The next step is to edit, and try again.