It's extremely beneficial if a person has made some sort of self-assessment, looked inward and self-assessed his or her skills, interests, and values. It is important that these three coalesce.
Choose jobs, including part-time and summer jobs, as well as internships, to give you as much information as possible about yourself, the profession, or the world. Analyze important aspects, positive and negative, of all the experiences you’ve had. What did you like about being treasurer of a club, for example? Did you like preparing a financial statement each month, or analyzing the data, or did you just like the title?
People who come to law school should have given significant thought to who they are and what they want from law school. This means that they should have done a thorough self-assessment, have a good sense of self and know what they're good at.
Guidance programs in high school and college could do more to help students evaluate what they've done, what they've liked, and why certain activities appealed to them so that students have a frame of reference for determining their skills, interests and values.
You cannot properly assess your needs without full-time work experience. It is very difficult to get sufficient understanding of what you do and do not like, let alone what the world of work is all about, without substantial work experience. Although you can eliminate some fields of endeavor as possible choices on the basis of your college and part-time work experiences, you are unlikely to get very far toward making a final choice. (Knowing that you dislike science does eliminate medicine from your future, but it does not help you choose among journalism, investment banking, and law.) Your twenties are the ideal time to sample the world of work, so take advantage of the opportunity.
You (and/or your parents) may be unwilling to take the risk that you will be unable to get into a worthwhile, rewarding, or prestigious position. As a result, you (or they) may feel the need to get into law school as soon as possible. This is wrong-headed for two reasons. First, your chances of getting into a good law school increase with real-world experience. Second, the greatest risk is that you will have entered the wrong field and be unable to get out of it successfully. Therefore, do not rush into law school. Work for at least two years, in one or more serious jobs, after college. Make sure law school is an affirmative rather than a default choice.