This post is the second one addressing the importance of picking a practice area as a first step to secure a summer or full-time legal job.
For different resources that could be helpful including a link to a NALP book containing skills and training required and narratives from practitioners about their daily work life, take a look at the information posted by the career development office at UC Berkeley School of Law. This site provides links to tools to help find out about different practice areas, employers in a particular practice area, a particular employer, etc.
If you truly have no idea what you want to practice, try to:
match your "major" to your background
relevant summer work experience you can leverage
relevant law school classes in which you excelled
undergraduate major
clinics, journals, other activities
choose a growing legal field
think about major legislation that has recently passed or will be and identify legal needs (i.e., health care, tax, securities, intellectual property)
consider practice areas with multiple paths for obtaining a job (Fed or State government, law firms of any size, industry, etc.)