How do I go about starting a business?
Just decide you want to start a business. Done. You're now in business as a sole proprietor.
Being in the US, you have the advantage of having a law system derived from British common law. Sole proprietorships and partnerships require no paperwork to be filed to exist.
However, they offer zero liability protection. You are not acting as an agent of a company, you ARE the company. You are personally and directly liable for anything that happens during the course of business.
If you work in a field where it is pretty easy to be sued (whether the cases are even remotely close to reality or not), it would be advisable to incorporate as an "S corporation" or a LLC (Limited Liability Company). You are not personally liable for anything done as an employee of the corporation unless you act outside of your role in the company.
Example:
You have a truck for your business. You accidentally hit a pedestrian on your way to a client's worksite.
The business will get the shit sued out of it, but you are not personally liable and your personal wealth and possessions are not at risk.
Now, let's say you were driving under the influence at the time.

Not only will your business be sued into the ground, so will you! You'll be taken to the cleaners.