Check out the recently published Writing Business Start-Up Guide. The guide will grow and expand over time, but for now, includes all important information about getting a taxpayer ID number instead of using your Social Security Number on your W9 Forms.
It also covers why almost all professional freelance writers should be incorporated as an LLC business type versus sole proprietorship. Then, it tells entrepreneurs how to setup a writing business LLC by filing Articles of Incorporation with the Secretary of State of your home state. (Technically, LLCs are formed without articles of incorporation, but people commonly refer to it in this manner anyway.)