Absolutely the best way to avoid standing in line! by yannniii
You can directly buy the Louvre museum ticket from a tabacco store called "La Civette du Carrousel", which is situated in the Louvre Galery. First, take the metro line 1 or line 7, then get off at "Palais Royal Musée du Louvre". Once you get off the metro line 1, you take the underground exit that takes you directly to the galary. If you take line 7, you will have to follow the direction to line 1 first, then once you are on the line 1 metro platform, you can then take the galary exit. When you reach the galary, you turn right and walk to the end of the hallway, you will be at the tabacco store. They offer one day admission tickets to the Louvre, Versailles Palace, and Musée d'Orsay. The date is open on the ticket. The price is the same as you would buy it at the entrance of the museum/monument. That means you can buy them in advance without standing in line at any of these monuments. They also sell museum passes for 2, 4 or 6 days (32?, 48? and 64?) . It is true that you can get tickets in advance from other places, like Fnac, Virgin Megastore etc, but they usually charge you extra!!!!
Once you buy the louvre ticket, you can enter the musuem through "Passage Richelieu" on the Rivoli street, which is about a 3-min walk from the tabacco store. It is a special entrance for visitors with tickets.