The Louvre
A few tips for going to the Louvre are:
1. bring exact change so you can buy tickets from a digital kiosk instead of the insanely long line.
2. Arrive underground through the subway/metro. If you come from above you're just in a longer line to get to the same place. There are two consecutive metro stops with similar names: "Louvre-Rivoli" and "Palais Royal - Musée du Louvre". To confuse tourists, the Louvre-Rivoli station is really fancy and looks like a museum. But the stop for the museum is actually Palais Royal - Musée du Louvre.
3. Pray that the Da Vinci code is not popular anymore. It's a made up story people, now get out of my way, so I can see the freakin painting.