Best way to get from newark airport to manhattan at midnight?

For 6 people the train doesnt make sense. Newark cabs are fine, but you need a van cab. I would book Allstate, Carmel or Dial 7 online. Or Uber. 

Do NOT take SuperShuttle - you could wait an hour for them to fill the other seats in the van at the airport, which they will never tell you - and then you get to drop off people at their hotels. Definitely dont take it back to the airport unless you want to get there 4 hours early - or risk missing your flight. 

There is a train from Newark Liberty International Airport to Penn Station in Manhatten. Takes about 1/2 hour. $12.50 for adult one way $8.75 for a child There is a train at 11:55pm and 12:45 am  

6 people may be pricey. There is always Taxi and Uber cars. Probably a set fare but not sure what that would be no need to buy tx in advance in either case.

Call a car service like Carmel.  Most have SUV's or Vans available and when you amortize the price across 6 people it's far more efficient than using SuperShuttle (which is awful and and a bad value too, even for one person) and a heck of a lot more comfortable than a train.  

I would 100% get an Uber black on arrival. Make sure it's an SUV. You won't wait long there are ALWAYS multiple Uber drivers in airports. Calling a cab ahead of time can't account for possible delays.

Call and schedule cab ahead of time (like a day prior). This Asian-owned taxi company offers reasonable fixed price service from Manhattan<--> Newark (New Jersey). Be sure to ask for a 7-sitter taxi, which can fit 6 people comfortably (no extra charge for luggage or for >5 people)

http://www.yelp.com/biz/good-luck-car-service-new-york

Agree with calling a black car service that has a flat fare or taking a taxi. With 6 it won't be such a great cost difference, and far less a hassle at that time of night. Best of luck and enjoy New York!

If your staying in a NY hotel, check for shuttles buses. Taxis can be expensive. Keep in mind that you must cross the Lincoln or Holland tunnel to enter Manhattan, cost for non ez pass customers is $14.00