Law schools look favorably upon mature candidates who have ventured into the "real world," overcome hardships, endured challenges, and generally acquired some perspective on life. This includes work experience before, during, and/or after undergraduate studies, internships, study abroad, advanced degrees, parenting, travel, or military service. Law schools value a wide variety of experiences, including volunteer work (can be very important to some law schools, especially those that stress service), internships, employment, study abroad, active membership or leadership in clubs and organizations, hobbies, or sports. Such activities need not be law-related.
Law schools prefer evidence of commitment and leadership in one or two activities over mere membership in a long list of organizations. They like to see that you care deeply about something worthwhile. It can be helpful if your activities in part take you out of the typical college comfort zone to deal directly with people who are not just like you. These "extras" that applicants bring to a law school are often discussed in the crucial personal statement.
Experience that is law-related can be a plus, but is not necessary. A delay between the undergraduate years and law school is often considered favorably. The average age of students at many law schools is 24 through 26.
Advice for freshmen: do not get overly involved in campus activities until you are sure you have established the habits to maintain a solid academic record. Be cautious. Activities cannot compensate for a relatively lower GPA (and especially not for a lower LSAT). Keep all of these issues in perspective.