The Louvre is an attraction that needs little introduction, but perhaps some hints and tips are a good idea.
We visited on a November Monday morning, arriving at around 10:30, hoping that the crowds wouldn't be too bad. Initial indicators were good, there was no queue for tickets or the cloakroom. I'd read that the Denon Wing first floor (Mona Lisa, etc.) is always very busy so we decided to head there first, however it seemed everyone else was already there. The whole wing was very busy, mostly with large tour groups and most of these apparently taking 'selfies' with great works of art behind them, or posing in front of paintings for their friends to take photos. The art was great, but the crowd was not; it was busy, noisy, and not a lot of fun.
After a while we left the first floor and headed to the second floor to find the Netherlands and Flemish paintings. This was like a different gallery entirely; it was quiet, spacious and people were enjoying the art, rather than posing in front of it for their own cameras. I'd recommend starting here and giving the 1st floor a miss entirely.
We finished up on the ground floor to see the Venus de Milo and Michelangelo sculptures. This area was busy, but manageable.
The entrance fee was €12. Although there are cafes, we didn't use them as we were so put off by the crowds. We found the cloakroom staff to be very unhelpful and surly in attitude.