This is the process in Floriduh:
If you are to be a Sole Proprietorship, a private individual doing business under a Fictitous Name -- shrinertech d(oing)b(usiness)a(s) Shrinertech Enterprises -- first you acquire a Fictitious Name registration form from the Secretary of State, Division of Corporations.
Then you fill out the form with your name, address, telephone number, the fictitious name of your business that you wish to register, and your social security number (because it also is going to be your business's tax ID number). You send the form back with a check for $50.
You then take out a public announcement classified ad in any newspaper somewhere in your county so as to announce to the world that you intend to do business under a name different than your own, and to invite any negative reponse to being about to use a name possibly registered to someone else. The ad must run for at least one week.
Once you receive confirmation your business name is registered, you apply for a municipal Occupational License and a county Occupational License.
Now you are in business legally.
Then you open a business bank account so you keep your personal finances separate from your personal finances, primarily bcause if you don't your accountant/tax preparer will think you're a twit and the IRS will not have to agree.
If you are to be a corporation:
You file with the Secretary of State, Division of Corporations your Articles of Incorporation that specify your business's name, address, number and type of shares to be issued, who's drawing up the articles, and who the Corporations Registered Agent is to be. You send the Articles to the State with a check for $70 and a transmittal letter.
When you receive the State's paperwork, fill out and submit to IRS Form SS-4 to obtain the Corporation's tax ID number (kinda like your social security number, but different), then fill out and submit to IRS Form 2553 to obtain sub-Chapter S status (better tax-related considerations and circumstances for a small business).
Once you get the corporation's tax ID number, go get your municipal and county occupational licenses and open a business bank account because you have to or the IRS will not like you very much.
Pay for everything by check (for the documentation), keep every single receipt (for the documentation), and find yourself an Enrolled Agent (for their ability to save you money and keep your ass out of trouble).
Procedures in your own state may be somewhat different. Ask a small businessman that you know how they had to do it.