Versailles is in Zone 4, so the t+ tickets that you use for inner Paris will not be valid. To get tickets, go to a station that RER C5 serves, and use to kiosk to select Versailles Rive Gauche. Alternatively, just go up to the ticket counter and say, "Château de Versailles" and hope the attendant speaks English (it's not guaranteed).
Also, be aware that it gets ridiculously crowded there. To avoid the crowd, it's best to get there before opening. However, if you're like us and not morning people, then I suggest going to the gardens first. There's no line for the gardens, and you can return to the palace later in the afternoon when the crowds begin to die down.
statue of Louis XIV
pretty sure this was already under construction last time I was here 14 years ago...
view of the gardens
The garden is quite large, so a lot of walking is required. There is a tram that can take you between points of interest, for a fee. There are also bicycle rentals, however the closest one is by the fountain, so you still have to walk there.
walking through the garden
artist restoring the walls