This Space Girl Pinup demonstrates the illustration process of this particular art style. Be sure to visit more often to see more behind the scenes art pages on how David Collins. 

David Collins always starts with sketches. This is a critical and foundational step in any illustration and art project. During this stage, the artist figures out all the necessary details such as proportions, poses, and generalized shapes. 
After the initial sketches, more definition and details are figured out. More refined lines are drawn to begin finalizing the foundation. 
Once defining the final sketching and design, David Collins takes the next step and "inks" the lines in to the black line art. This actually is David Collins's favorite part of the illustration process. 
The color process. This is where the colors, shading and effects are added to complete the illustration.