Visit the Department of State's Starting a Business page. The Small Business Development Center is also a great resource.
1) Write a business plan
Here are a couple of posts I've devoted to this subject - Business Plans: A Quick Guide and Piecing Together the Business Plan.
The Small Business Administration has a handy page about writing a business plan.
2) Decide on a location
Sunbiz.org has a page devoted to selecting a location with handy links about demographics and economy.
3) Choose a business structure
First, read this great article on how to choose your business structure - click here to read PowerHomeBiz's Choosing Your Legal Structure.
Once you've done that go to the Division of Corporations site, which is where you can search and file corporations, LLCs, LLPs, fictitious names, etc.
Read the Start-Up Kit for New Business Owners.
5) Licenses & Permits
Business license information can be found here.