I go to school there. Where are you staying? Down town or farther out?
The french quarter is where you'll probably want to see. The difference between it at night and during the day is, well, day and night. During the day there's beautifal art galleries and nice little shops to go shopping in. At night it's the biggest party you've ever seen. Here's one word of advice though...
Crowds = safer
Do NOT go wandering someplace at night alone. The city is fine if you use your head, and you can get yourself mugged easily if you don't, or worse.
I would say try and see a show at house of blues if something good is playing. Hit up some parades (this year is my first mardi gras too, w00t!) and just have a good time. You should enjoy the weather, it was mid 60s today and not a cloud in the sky. It does get chilly at night though and rain is always a possibility. Our weather changes quickly, if you don't like it wait a few minutes.
Anyways, for food, try red beans and rice at least once. There's alot of good cajun food but pretty much everybody likes that. There's a good place called "The Gumbo Store" somewhere in the french quarter that I liked alot. Prices aren't too bad, even us poor college students eat there once and a while.