If you want to get a tag but don't own a car, you can still sign up online. This is what the rep told me to do. Falsify info on your cars plates, make and model (for the plate# write the first two letters of your family name with the last 4 digits of your cell number, year: current year, make\model: choose any), and once you have an account just log in and remove that car from your profile.

For those travelling the Lakewood - Brooklyn route often:

Sign up for a NY EZpass from either the NYSTA (Thruway) or MTA to avoid the $1 monthly fee. NJ/NY Port Authority charges the monthly fee.
The point of getting the NY and not NJ is to make some frequently travelled tolls cheaper.  The Verrazano bridge will be $6.55 instead of $10.17, the battery tunnel will be $5.33 instead of $7.50, the discounts you will lose out on for not having the NJ pass are very minimal (a couple of cents on the NJTP during peak hours)

Add the following discount plans:
Port Authority Staten Island Bridges Plan (PASI), which makes all PA bridges (Outerbridge,Bayonne,Goethals) $5.25,when crossing 3 or more times a month. There is nothing to lose as if you don't travel 3 times they simply adjust it to charge you the regular

You have to add carpool to your plan but if you end up going less than 3 times in the 30 day period you pay the full price for the toll (a little cheaper cause your using ezpass). I believe it takes 24 hours from when you call for it to activate and its per 30 day period not monthly.

EZP rate.
Port Authority Carpool Plan, $5 if you have 3+ people in the car.

NOTE: Sometimes signing up for the EZP with carpool on the plan you initially order, can cause a Port Authority EZ Pass to arrive (which has a monthly fee). It's therefore suggested to order a standard plan, wait until you receive your EZP (hopefully the MTA or NY Thruway  EZP versions) and then tack on the Port Authority Carpool Plan afterwards.   

Edit 5/19/2014: You can add PACP and PASI yourself on the website (in case the phone hours aren't convenient or you just plain don't like calling in general). Log in and choose "Plans" from the links on the left side of the page.

Another plus to having MTA issuing authority is that you can use PPT. Under this plan, you can keep a $0 balance in your EZ Pass account, and have tolls deducted from your bank account at the end of each day (by ACH). Downside is no miles for paying tolls, credit card is only a backup for when the ACH fails. (And if ACH fails even once you lose PPT plan and have to keep a debit balance in your account, so you can't have the miles & PPT :) )

Edit 12/28/2015: In order to ensure that you are enrolled by the MTA agency (see above), when you sign up, you should give an address in NYC (not just NYS). If you don't live there, ask a friend who lives there to receive the tags for you, and use his address. Afterwards, you may change the address to your home address in NJ (or wherever), and add whichever plans you want. This was suggested to me by EZ Pass, and it works.

To return an extra tag for NY MTA Authority:

Please return your tag(s) to:
P.O. Box 149001
Staten Island, NY 10314
along with a letter that states your Name, signature and E-ZPass account number.
For further assistance please contact (800) 333-8655 to speak with a Customer Service Representative.