Versailles Private Tour

Book your Kings State Apt ticket at the time you want to enter Versailles. Once this tour is done, they will take you to the start pf the regular palace tour. By doing this, you will avoid the huge security line to get into the regular palace tour. The Kings State Apt tour has a separate entrance and Its own security line. Of course make sure you purchase the regular palace tour and have the ticket on hand for when you finish the Kings apt tour. Just make sure you wear comfy shoes and bring snacks!

yes, book it separately from the entry ticket. If you have the Paris Museum Pass, then you already have your entry ticket, so you only need to book the Private Tour. We just got back and did this tour. It was great and it gets you into the Palace without waiting in any lines, which is priceless.
It took us longer to get to Versailles then we expected and actually missed our pre-booked tour. We looked at the line to get in without the tour and nearly cried. We were able to rebook a different time slot about an hour and half later (of course, paying again!) but that still got us in sooner than the line just for the palace. And the tour was quite interesting.
My point is to leave from Paris sooner than you think. We left at 8:00am for a 9:30 tour, which we missed, arriving at 9:45. For some dumb reason, we arrived at the train station to get on the RER and had a 42 minute wait for the next one. That really threw us off for our timing. So frustrating. But it all worked out in the end!

As the previous commenters have described, you'll need a main entry ticket. You can choose the time that your "visite guidee" will end, or get an untimed ticket. Either way, the nice thing is that the visite guidee will leave you off inside so you don't have to stand in the huge line in the courtyard. BTW, be careful walking on the cobblestones as they can be slippery!

The entrance for the visites guidees is to the right; the opposite side of the courtyard from the main entrance with airport-style security that the general public has to go through.

Our tour was great. Our guide spoke excellent English, was very knowledgeable, and was also interested in what little expertise some of the tour-goers had relating to various aspects of the chateau and the French royal family.

Thanks everyone.
We were going to skip the museum pass this time, but I think the best alternatve may be to buy the Guided tour online now and pick up the Paris Museum Pass when we arrive at CDG. We'll still probably get our monies worth. I mean can I really go to Paris and not make a trip through the Louvre? Or the Orsay?