Logo design can begin at any stage during your project but ideally you would want to have at least the script complete and a few pages of art.
After an initial discussion (via email or on the phone), we can reach an understanding of your project's goals, the style of your comic, the type of logo you require for your project, your budget and a deadline date.
If you're happy to move forward then you would supply me with any relevant material that would help me to understand the comic better. I would then create a 1-4 basic variations of the logo and return them to you for approval. You would need to chose the logo style you prefer and then I would continue to develop that logo until we are both happy with it.