We bought the Fortait Loisirs for €19,20 at the RER C station which included return train tickets and entrance to Versailles.
We took the RER-C train from St. Michel. Any train that starts with a "V" will go to Versailles. The train ride took just over half an hour. When you exit the Versailles train station, turn right then left at the first main road… only a 5-10 minute walk. There are little kitschy souvenir shops and cafes along the way. Outside the main gate, there are stands selling beverages and paninis, even a crepe stand. The options for eating once you enter the Palace are pretty meager (one cafe and one restaurant, I believe). We preferred having a picnic lunch in the gardens.
Unfortunately we headed out later than we wanted and arrived at Versailles at 11 am (guide books recommend arriving by 9 am to beat the crowds) where we were greeted with an insane line, coming out the building and almost reaching the main gate. We waited in line for over one hour but fortunately it was a sunny day and I can only imagine how miserable it would have been waiting in the rain (it started to rain later that afternoon).
The Chateau was completely packed and we could barely move in the Hall of Mirrors. After we toured the State apartments and viewed the Dauphine apartments, we went outside and walked through the Gardens where we sat and ate our picnic lunch.
Later we walked over to the Grand Trianon which has recently been beautifully restored. The Grand Trianon was built for Louis XIV as a retreat from the "hardship" of court life and also a place to be with his mistress privately. It is placed at the very far end of Versailles; a good 20 minute walk from the main Palace.
Unfortunately during our visit, the Petit Trianon (Marie Antoinette’s private hamlet) --- which I would have loved to have seen, as it's just so different from the rest of the Palace -- was closed for renovations. I have since read that it reopened in October 2008. Swiss watch maker Breguet donated a considerable amount to the restoring of the Petit Trianon to its former glory. Breguet has a long history with Versailles including being the favorite watch maker of Marie Antoinette herself. There’s no doubt that Petit Trianon has been restored so beautifully that even Marie Anotoinette would approve of. I hope to have a chance to see it soon.
The Palace is closed on Mondays so avoid going on Tuesdays and even Sundays if you can, as it will be even more crowded and crazy.