How do I learn to act, think, and carry myself as a CEO?

In the next year, I will be setting up my own business as a freelance business writer. I will be a one person operation and will be functioning both as management and personnel. I view myself as a quiet and competent professional. But now I will need to learn to think and act as a CEO, especially since I will now have to attract customers. In the companies that I have worked for, I noticed that the CEO's thought, acted and carried themselves in what seemed to me to be a certain way. They were obviously leaders, but there was also something in the way that the behaved that set them apart. I would like to know what that is and how someone would acquire those skills that I observed in CEO's. Thank you for taking the time to read my question and I look forward to reading your responses.