There are three railroads that use Penn Station -- NJ Transit, Long Island Railroad and Amtrak. Make sure you are in the New Jersey Transit area and ticket booths. You can ask the ticket seller what track the train leaves on. They also have TV screens and a big board that give departure times and track numbers. These will identify the train by its final destination and departure time, which most probably is NOT Linden, probably Trenton or Rahway. Make sure you know the departure time of your train. See scheldule here: http://www.njtransit.com/pdf/rail/r0070.��Your train is Rail not light rail. Also, the ticket machines DO take cash.
When you go to the NJ Transit Concourse at Penn Station you can either stand on line and purchase you ticket, or purchase them at the ticket machine. If you re purchasing you ticket from the ticket window, just let the sale person where your going.By the way the one way fare from NYC to Linden, NJ will cost you $6.50 ($13 round trip).Good luck
When you get to Penn Station, follow the signs to NJ Transit (your best bet would be the entrance that is right in front of MSG s entrance, the one that s in front of the Border s. All the hobos are hanging out at the newstands to the left and the right of that Penn entrance; the taxi line is there too). If you go to the machines, you need a credit/debit cards. If you go on the line, the accept cash, credit, and debit. You want a roundtrip ticket; off-peak, if possible, but be wary; you have to pay extra if you buy an off-peak round trip ticket (it ll say ORT on the ticket) and ride during rush hours.You can pick up a schedule for the Northeast Corridor line (the abbreviation on the electronic board that tells you which track to get on is NEC; the destination of the train is Trenton). That line is the line you need to get to Linden. You ll need a local train; the express trains bypass a lot of stations to Trenton. Make sure you re on a local train that s heading to Trenton. You CAN buy a ticket on the train, but it costs, I think, $3 dollars extra. I ve never been to the Linden station, so you re on your own for that. Good luck!