I have been to 2 museums so far (the D'Orsay and the Modern Art Museum at the Pompidou Centre) and both times, I got in for free! No real tip here; I was just pretty stoked with the whole thing.

Ok, an actual tip: Most of the museums are free for 18 year olds and under, and discounted for 25's and under. Also, some days they let 25's and under in for free. And on the first Sunday of every month, all the museums are free for everyone.

But I'm pretty sure it was me smiling at the ticket guys that got me in for free.