<font face="Verdana, Arial, Helvetica, sans-serif" size="2">Originally posted by B747-437B:
Simple.
NJ Transit train from NY Penn Station to Newark Penn Station. (US$3.30 fare - 15 minute ride)
Follow the signs to the bus stops and take the NJ Transit bus route number 62 heading towards Perth Amboy. It stops at all three terminals at Newark airport. (US$1.10 fare - 20 minute ride)
Total cost : $4.40
Total travel time : 35 minutes</font>
This would be the way to do it, but it's going to be a pain if you have check-in sized luggage to haul around as you transfer about.