The parking lot is located at exit 15X of the NJ Turnpike. Parking is $10 for a full day and $5 after 4 P.M. and on weekends. There are also monthly pass rates, in addition to Giants, Jets and Meadowlands events rates. With these prices, I cannot understand people who drive to NYC through the Lincoln Tunnel.
Plan to park your car at least 15 minutes before the train gets in because to get from the lot to the track, you will have to overcome two NJTransit wonders of the world:
1. The elevator from the street level to the concourse: This elevator can easily win the Guiness book of records for the slowest elevator ever. If you're feeling inpatient, you can always walk down the street-level corridor and take the escalators.
2. The lack of ticket vending machines (NJTransit calls them TVMs): Someone very smart in NJTransit thought that it is a better idea to have most of the TVMs after the ticketing gates and not before them, leaving passengers who want to buy a ticket with one TVM in each side of the ticketing gates.
You can use hopstop to plan your subway adventure once you are in NYC.
Getting back from NY Penn Station to Secaucus Junction is easy. Check the display boards for NJ Transit trains. Every train that has SEC next to it stops at Secaucus Junction. Gate numbers are posted about 10 minutes before the trains' departure times. Secaucus Junction is always the first stop after Penn station. And don't forget to buy your ticket before boarding the train since there is a $5 surcharge for buying tickets on the train. And one more thing: Hold on to your ticket when you exit the train at Secaucus Junction. You will need it to get out of the gates at the train station.
BTW: Secaucus offers great shopping opportunities, and there is a free shuttle to the outlets from the Junction.
Added Aug 27th: The NYC MTA has published some info on taking the train from NY to the Giants and Jets NFL football games in the Meadowlands.
Added Sep. 19th: Connecticut Jets and Giants fans will be able to enjoy direct service to Giants Stadium aboard three trains. Passengers will travel on NJ Transit double-decker trains in a joint effort by Metro-North Railroad, the Connecticut Department of Transportation and NJ Transit to provide trains for fans from Connecticut and Westchester County going to games. Information can be found here.