Career exploration involves knowing everything about the occupation, the businesses that employ them, and the industry in general. You also will benefit from knowing the local labor market to determine where the jobs are in your area.
To research occupations, go to the O*NET website: http://online.onetcenter.org - Click on the "Find Occupations" heading then type in a job title in the "Search by" box. You may also find jobs listed in different career categories in the "Browse by" box; scroll through the various categories then click on "Go" to see the list of jobs...then click on the job title to read the description and other information about the job.
More general but comprehensive job descriptions are found in the Occupational Outlook Handbook.
The State of California Employment Development Department publishes hundreds of Occupational Guides: Link to Guides
Here are some other interesting resources including occupational video sites...
Videos of professionals discussing their careers: Careers Out There
Occupational profiles with people answering questions about their careers: The Career Project
Not sure what questions to ask? Questions to Ask During an Informational Interview