How many days ahead of a hearing do I have to serve the papers in New Jersey?

I am not sure exactly what the question is. If there is a hearing already scheduled based upon a motion or petition that was filed by a party, you have to file papers at least 16 days before the hearing date to give the other party time to answer (28 days if it is a motion for summary judgment).  Reply briefs need to be filed at least 8 days before the hearing date. However, if you are talking about a trial, then there should be a pre-trial conference scheduled (at least in Law Division, these do not apply in Special Civil) at which time the parties list their trial exhibits and have them exchanged with the other side or a date is scheduled at that time at which all trial exhibits should be presented. So this answer depends upon the type of hearing you are talking about as well as which court this is in.