For EWR fliers who drive and park in short term parking:
How do you handle pre-booking when you don't know if you are departing from A or C? Looking at my flight, it seems to leave from A or C depending on the day. Any suggestions?

To clarify: I am looking for UA specific guidance (e.g., is there a way to determine with greater accuracy which terminal or is there a trick to use when booking parking?).