I don't care much for driving into NYC and will take a commuter train if I'm out in the suburbs and just going to the city for a day.
Suggest sticking to one of the lines with more frequent schedules, and picking a train that goes direct to either Grand Central from
MTA Metro-North Railroad , or direct to Penn Station from
New Jersey Transit (read the schedule closely to make sure you don't have to transfer at Newark or Secaucus to an already full train that came from somewhere else).
Then read the station information closely to ensure there's enough parking reasonably easty to get to. (A couple of examples might be Hamilton and Ramsey-Route 17 on NJT.)