The Louvre is an amazing museum that lives up to its world-famous reputation.
I have visited this establishment four times in the past eight years. Every time I even see the glass pyramid, I am struck with affection and admiration for both the vast collection and colorful history of the buildings.
First, the basics. The Louvre, along with all the national museums, is open free to the public on the first Sunday of every month. [My second visit was on one of these days, and it was a madhouse. The line went on forever and even looped back around, out into the courtyard. Inside, there were huge groups of tourists clamoring to get to the big stuff--the Mona Lisa (nearly hidden behind the throng and their camera flashes), the Venus de Milo, the Nike.] The main entrance is through the infamous glass pyramid out front. But the best way to get in is through the Rivoli door or Rivoli stop on the Metro (not the Louvre stop). That way takes you into the underground mall, complete with Virgin megastore and food court. [Incidentally, my 13-year-old cousin was there my fourth time, and she wanted to get burritos. At the Spanish place. She didn't understand how Mexico and Spain have different cuisines.] Visit the several shops/bookstores to find posters, 8x12prints, postcards, mousemat, calendars, puzzles, notebooks, bookmarks and more, featuring the more famous images in painting and sculpture. You will be able to find images that aren't in the Louvre but are famous; there are reproductions from the National Gallery in London, the van Gogh museum, the Rodin museum, the Musee d'Orsay, and more.
The best time to go is in the afternoon or evening, when the throngs have receded. One night a week it is open late.
The collection itself spans centuries and continents with apparent ease. Pillaged, seized, and bought, the pieces tell a complicated story of a growing global commerce.
Some of my favorites include Nike, Winged Victory (I bow a tribute to her every time I'm there), the Botticelli frescoes (even though the figures all look the same), the collection of ancient Greek, Egyptian, and Etruscan work (there is a display of the temple of Zeus in Olympia, in Greece, that I had been in a few weeks prior to my most recent visit), and the Jacques-Louis David paintings (notably the Coronation of Napoleon). The Napoleon Appartements are a startling example of the splendor royalty lived in. The dining room seats over forty, and it has hidden doors through which the servants could disappear. The rooms are filled with red velvet and gilt chandeliers, furniture, and other decorations.
In conclusion, this museum is truly astounding. I urge you to visit it many times, to learn about the history of the chateau itself, to learn about the works held within its walls, to find new things each time, and to not be discouraged by the tourist-infected hallways and rooms. Ignore them and gawk at the art.