Although you can drive yourself to the DMZ, I highly recommend taking an organized tour instead. Not only will you get a detailed history lesson, but you will not have to stop at the numerous checkpoints along the way. Some locations you'll want to check out don't allow individual visitors anyway.
The following are some places where you can book guided tours in English. Most of the tours cost W70,000 or less (the USO tour is only W39,000), last most of the day or all day, and include lunch.
The Panmunjeom Tour Information Center provides travel and tour info to Panmunjeom and the DMZ. It's located in the Lotte Hotel in Seoul (on the second floor of the main building in Sogongdong; tel. 02/771-5593; www.panmunjomtour.com). Take subway line 1 to City Hall Station or line 2 to Uljiro-Ipgu Station. The Panmunjeom Tour (which includes the Mt. Odu Observatory, the Unification Bridge, and Camp Bonifas) lasts from around 9:30am to 4:30pm and costs W70,000, which includes lunch.
The Korean Tourism Organization (KTO), B1, KTO Building (T2 Tower), 40, Cheongyecheonno, Jung-gu, Seoul 100-180 (tel. 02/7729-9600; http://english.visitkorea.or.kr; daily 9am-8pm), offers two different DMZ tours. The first tour takes you to the DMZ and the Third Infiltration Tunnel. Starting at Incheon Airport, you will see the tunnel, Mt. Dora Observatory and Station, and Imjingak and the Bridge of Freedom before returning to the airport. The tour lasts about 5 1/2 hours and costs W74,400, including transportation, admissions, and lunch. The second tour goes along what they call "the trail of peace and unification." It also starts at Incheon Airport and goes to Mt. Ohdu Observatory, Imjingak and the Bridge of Freedom, the Bell of Peace, and the Freedom Train, and back to the airport. The tour is W70,000, including transportation and admission, and lasts 4 1/2 hours. The USO also offers a Panmunjeom/DMZ Tour (with a markedly American perspective), which costs W20,500 to W39,000 and includes Panmunjeom and the Third Infiltration Tunnel. They ask that you reserve your place at least 7 days in advance. Call or e-mail them for available tour dates (tel. 02/724-7781; www.uso.org/korea).Grace Travel also offers Panmunjeom tours from Seoul. Their morning tour goes from 8am to 2:30pm and covers Imjingak Park, the Bridge of Freedom, the DMZ Theater and Exhibition Hall, the Third Infiltration Tunnel, Mt. Dora Observatory and Station, and a ginseng center or amethyst factory, and goes past Unification Village. For this tour, costing W46,000, they'll pick you up from your hotel but drop you off at Itaewon (tel. 02/332-8946; www.triptokorea.com).
Warning: For all tours, remember that you must have your passport with you. Dress conservatively -- that means no crop tops, flip-flops, or sheer clothing. Do not wear anything displaying communist insignia -- and leave your Che Guevara T-shirt at home. Also, photography is restricted in certain areas, so be sure to ask before taking pictures. All video cameras are forbidden in restricted areas, so it's best not to bring one at all.
Note: This information was accurate when it was published, but can change without notice. Please be sure to confirm all rates and details directly with the companies in question before planning your trip.