How Does the Paris/Museum Pass Work?

I only have used the Paris Museum Pass. When you plan to first use the pass, you will write down your name and the date on the pass. Do not write a date on it until you are absolutely sure you are ready to use it. When you enter a museum, you simply show them the pass, they look at the date that you wrote on it and figure out if it's valid. You can easily purchase the Paris Museum pass at any of the sights. I recommend one of the lesser visited sights, such as Napoleon's tomb because the line to buy the pass will be virtually non-existent. You do not have to use it that day or even at that sight.

You can also buy the Paris Museum Pass at CDG.
In May I was in Paris 11 days, bought the 6-day pass, and planned my itinerary so that I would be in the city and using the pass the first 6 days, and then do day trips (not covered by the Pass) after the initial 6 days spent using the pass.

The Paris Museum pass works the way Stephen explained it, and how it's explained on the website for that pass:

http://en.parismuseumpass.com/rub-t-how-to-use-it-19.htm

The attendants at the entrances to the attractions it covers will check that first date to make sure the pass - whether 2, 4 or 6-day version- is still valid.

Honestly, almost no one recommends buying the Paris Pass, which includes the Visite travelcard for transport. I've never been able to figure a way to come close to breaking even on that one: it's an extraordinary price for the transport piece. Getting around is less expensively done with booklets (carnets) of 10 tickets for only 14.10 euro. You can buy a the Museum Pass, a few of those carnets, pay cash for a couple of attractions and still come in under the price of the Paris Pass.

Yes, buy the Museum Pass when you arrive in Paris. Either do that at a less-visited attraction with no queue, as Stephen suggested, or any others of the outlets listed: click the tabs for "Airports" and "in Paris" on this page:

http://en.parismuseumpass.com/rub-t-points-of-sale-3.htm

I bought the six day Museum Pass last week, and visited nine museums in that time (plus Eiffel Tower and two galleries of Museum of Natural History, which weren't covered). Definitely wait until you get to Paris to buy. I had intended to get mine at CDG but was in a hurry. Later that day I was doing my own walk around and stumbled over the kiosk at Notre Dame, no line at all.

The so called 'Paris Pass' is not a pass if by that you think one card to do museums and metro -- it is simply an envelope with the ordinary museum pass and the ordinary Paris Visite which is a tourist rip off transport pass which 95% of the time is a very bad deal.

The Museum Pass is a good idea for a first trip when lots of museums and monuments will be visited; you get to use better security lines many places and you can enter the same museum repeatedly which is great for the Louvre in particular. You can also sample places you might not otherwise visit.

Museum entry is by inspection by an actual human -- no swiping needed.

Be careful writing your dates down. If you start you pass on September 8, 2015, and write down the American version of 9/8/15, they may think you are trying to use an old pass from 9 August.

I have taken to writing dates with the month spelled out when dealing with European institutions e.g. August 1 2015 and not 8/1/15 or 1/8/15 -- that way I don't inadvertently use the American format.

I have taken to writing dates with the month spelled out when dealing with European institutions e.g. August 1 2015 and not 8/1/15 or 1/8/15 -- that way I don't inadvertently use the American format.

Great idea but doesn't work with the Museum Pass: the spaces only accommodate numerals (i.e. today's date would be 31/07/15)

Practice writing dates as 1 Aug 2015 instead of Aug 1 2015 -- think of it as the logical order day-month-year (smaller units to larger)-- so the numeric version works in Europe.

Often the ticket takers who look at your pass have a date stamp and will do it for you. They certainly have a pen. If nothing else, play the dumb but polite tourist and they'll write in the date.

It's really not that hard: the website shows you exactly how to do it, and you only have to do it ONCE.

Are we really having so many posts about writing a date? :)