"Official" directions (from ETS itself) can be found at this link.  The following directions and map may also be helpful.

To get to ETS from any direction, the easiest way (though not necessarily the quickest) is to go to the intersection on Nassau Street circled on the map below.  It's at the south end of Nassau, near the very large war memorial that dominates the area.  Turn there onto Highway 206 north (Bayard Lane).  Drive then a short distance to Cleveland Lane, and turn left.  (If coming from the north on 206, turn right on Cleveland Lane.)  After about a half mile, there is a traffic light where Cleveland Lane becomes Rosedale Road.  Continue straight ahead about 2 miles on Rosedale, then watch for the sign on the right for the Educational Testing Service.  Turn right.

To get to the Conant Hall meeting room:  

Follow the signs to Conant Hall, but do not turn at the sign, because you have to go around to the back of the building.  To do so, drive on, past another driveway, then past an open area with a large flagpole in the middle, then make a right.  There is a sign there with "Security" at the top.  Drive to the next right (where there is also a sign to "Security") and turn into the parking lot, stopping temporarily at the end of the lane.  You will see, slightly to your left, a sign for "Wood Hall."  Now look carefully to the right for a red sign saying "Conant Cafeteria."  (It is partially blocked by trees and, quite possibly, lost astrologers.)  This sign marks the entrance for our meeting room.

Find a parking place, walk back, through the cafeteria entrance; turn right, and then left, past rest rooms on the right, to the end of the hall.  The meeting room there is marked "Lounge A." 

To get to Anrig hall, Room #P-016:  

Make the usual right turn into E.T.S. Then make the first right turn thereafter. The first building on the left will be Anrig Hall. Room P-016 is clearly marked on the first entrance on the left.