This is a list of some important steps to take to establish your business as a legal entity.
Prefer paper?
Choose the right entity structure for your practice
Determine what business structure is best for your needs
First, check out your state's guidelines on professional entities. Some states require you to operate as a professional entity (PLLC or PC) instead of a generic equivalent (LLC or Corporation). Here's a state-by-state rundown.
After figuring that out, decide whether an LLC or Corporation is right for you. Basic rule of thumb: if you want to add an additional physician/partner at some point a PC will be easier. If you know you'll stay a one-doc shop forever, a PLLC could make your life easier since it allows pass-through taxation. Basically all business revenue "passes through" the LLC to you and is treated by the IRS as personal income. This eliminates the need to do an independent corporate income tax return.
You may likely want to confer with an accountant to make this decision, or look at other nearby practices.
Draft Articles of Organization/Incorporation
Draft an operating agreement/bylaws for the company
Find a registered agent
Incorporate the business through your state
File a DBA with your state
Apply for your Employer Identification Number (EIN)