To get things started, I decided to post one of my older tutorials (on the image above ^) done about 2 years ago. I will have more updates soon.(The write-up is old. I will have this replaced with a newer tutorial later this week).
Step 1: The Sketching
I have been doing my sketching directly on the computer recently, because it allows me to work faster and make adjustments much, much easier. Since this is an action oriented illustration, I like to consider triangular composition to enforce movement.
Step 2: The Inking
Below is an image of all of my inking tools that I used for this illustration. I like using fine brushes for my finished work because it brings the drawing to life and makes the illustration look much more interesting. When I apply my black shapes, I constantly place either tracing paper on top of the image or blur my eyes out to see how the overall shapes read. I strongly believe that if an image does not work as a black and white, then it will not work as a color piece either. In this case, I wanted to create a circular pattern of my blacks to contrast the triangular composition of the image and also lead the eye around the image.
Step 3: The Flats
I start laying in my flats working in CMYK using Adobe Photoshop at 600 dpi. I set the line layer to Multiply and use the white canvas layer underneath to lay in my flat shapes. As I am laying in the colors, I use the "Selective Color", "Replace Color" and "Hue/Saturation" options to adjust the colors to my liking. I like to stick to a maximum of 3-4 colors in all of my work because anything beyond that becomes visually too busy and unbalanced.
Step 4: The Shadows
After all flats have been tightened up, I start laying in my shadows by using the lasso tool to create various shapes and fill them in with the darker value. This step is one of the fastest steps in this process.
Step 5: The Textures
The final step is to add some texture to the piece in order to make it look less flat. I either scan textures, or in this case found some free dirt textures at www.mayang.com
I lay the textures on top of the image and mess with the opacity of the texture layer and also use a soft eraser to define my edges and clean up the image.
7-8 hours total. I hope this was helpful.