Some of the laws that the Berkeley Heights Public Library has a copy of are the Berkeley Heights municipal ordinances (town laws) and the New Jersey Statutes (state laws). Both are available online, but the state laws in particular are easier to use in paper (its index is much more helpful than the keyword search results you get in the online version). The Statutes are kept in the study alcove in the reference room and you can ask for the ordinances at the reference desk.
Sometimes people are looking for case law, which are laws decided by court cases. "How do I get LexisNexis/Westlaw/Shepard's?" they ask.
The law libraries at the Union County, Morris County and Somerset County Superior Courts' law libraries have public access to LexisNexis. Berkeley Heights is in the Union County Superior Court's jurisdiction, but some people prefer the drive to Somerville or Morristown instead to do research on NJ law. You should always call ahead to find out the hours of the law libraries. Also, the Information and Community Relations Center of the Superior Court of New Jersey, Essex Vicinage (in Newark) has LexisNexis.
LexisNexis and Westlaw are competitors, and even though law librarians prefer Westlaw, that's not what seems to be available around here. Shepard's (which tells you if a case is still valid) is included in LexisNexis.
Some people come to the library looking for legal forms. If it's a form you need to file in a court, try NJCourts.com, the website of the NJ Judiciary. Their Self-Help Resource Center has many forms for people who represent themselves in court. The Self-Help Resource Center of the Union County Superior Court (on the first floor at 1143 East Jersey St. in Elizabeth) also can help with forms. Their hours are Tuesday - Thursday, 10 am to 2 p.m. BHPL has many books published by Nolo that come with sample legal forms. Look in the 340 section of nonfiction for those.
If you need a lawyer, Union County Bar Association and the Morris County Bar Association both have lawyer referral services for a small fee (a max of $50 for the first 30 minutes of consultation in Morris County). If your income is low enough, you may qualify for help from the nonprofit Legal Services of New Jersey. The best way to get in touch with them is through their hotline, 1-888-576-5529, Monday through Friday, 8:00 a.m. to 5:30 p.m. Their peak hours are in the morning, so try to call in the afternoon to reduce your wait time.
*Addendum (posted on 7/14/10): Only a few days went by after this post before I had another law question, this time from someone wanting to call the U.S. District Court's law library in Newark. Anne pointed me to the New Jersey Lawyers Diary, which is in the BHPL legal reference collection in the alcove, to answer this question.