New Orleans Mardi Gras
The festival is rooted in the ancient European Carnival traditions. It marks the final celebrations before the period of fasting during Lent in the Roman Catholic Religion, although New Orleans Carnival is enjoyed by people of any belief.
For locals, "Mardi Gras" strictly speaking is only the last and biggest day of the Carnival season, "Fat Tuesday". Visitors less clear on this distinction sometimes call the whole New Orleans Carnival season "Mardi Gras". The final big day is thus sometimes called by the (technically redundant) name "Mardi Gras Day".
After spotty earlier festivities, parades roll every night starting 2 weekends before Mardi Gras. Things kick into high gear the weekend before Mardi Gras, when the population of New Orleans more than doubles (book a room well in advance!). There's an all day party along the riverfront downtown on Lundi Gras ("Fat Monday", the day before Mardi Gras) followed by more parades that evening, and just when you think things couldn't get more wild, the climax of Mardi Gras Day takes Carnival to an entirely new level.
Wearing a mask or costume on Mardi Gras Day is highly recommended by Mardi Gras Veterans, one becomes part of the party, rather than just watching it. Veterans also start the party in the morning on Mardi Gras Day, even if you aren't usually a morning person. Mardi Gras ends promptly at midnight Tuesday.
The next day is Ash Wednesday (nicknamed locally "Trash Wednesday" from the debris left in the streets from the parties), the start of Lent. Wearing Mardi Gras beads during Lent will mark you as a tourist ignorant of local customs.
Date of Mardi Gras
Mardi Gras parades are a big attraction. Many locals have their favorites and by not following the crowds, you can often get a better perspective on the Big Easy.
The parades are put on by private organizations known as "krewe"s; they do not receive any government or corporate sponsorship.
Watching a parade in New Orleans is a participatory party; crowds dance to the music of the bands and clamour for "throws". Throws are the trinkets thrown from krewe members on the floats to the crowd, including plastic beads and cups (often decorated with the emblem of the krewe), "dubloons" - small aluminum discs like a souvenir coin, and various toys and gee-gaws.
Pick up the Mardi Gras Guide magazine, or consult the newspapers for parade scheduals and routes. Note that many of the smaller parades, marching krewes, neighborhood pagents, Mardi Gras Indians, etc are usually not listed in these scheduals.
Other parades of interest
The nights of the week leading up to Mardi Gras, in addition to the days on the weekend before Mardi Gras, have numerous parades.
There are dozens of small neighborhood krewes and walking clubs, including:
Pete Fountain's Half Fast Marching Club headed by the city's most famous Dixieland clarinetist who leads his band on a small float, the Half Fast wind through uptown down to the Quarter on Mardi Gras Day.
Mardi Gras Indians, Bourbon Street, Lundi Gras in Waldenburg Park, Arrival of Kings of the Zulus and Rex, costume parties, balls, block parties
Family Friendly Mardi Gras
While some visitors think of Mardi Gras as a "Girls Gone Wild" event, for many locals and visitors Mardi Gras is kid-friendly family fun. Stay away from the rowdies on Bourbon Street; catch the parades Uptown on Saint Charles Avenue anywhere above Lee Circle up to Napoleon Avenue (Note: on Mardi Gras Day Zulu parades only on the portion of the route from Jackson Avenue down). Most kids love the excitement of catching the beads; for safety just make sure they don't try to run up too close to the floats. On Lundi Gras (the Monday before Mardi Gras), the festivities in Waldenberg Park (along the Mississippi by the upper French Quarter just below Canal Street) includes a children's stage. On Mardi Gras Day dress the family in matching costumes to be thrown extra beads and have extra fun.