In a nutshell, the first thing that you will need to do is draft your Articles of Incorporation and file them with the state. A quick search on google could probably give you examples of how to write them. You would file with the application that can be found
here. In addition, be sure to check out
http://www.ss.ca.gov/business under corporations.
Note... filing this does not entitle you to tax exempt status. You will need to fill out the proper IRS forms. For a list of requirements for that, check out
this link.
As far as how a booster organization operates... your best source of knowledge will be to actually attend a booster meeting or two at another school.