125.7 (KJFK Rober) is probably your best choice. This frequency is active 24 hours a day. All the others only become active when traffic gets busier. During the day 125.7 handles inbound flights from the east. 128.125 handles inbounds from the south, etc. When it gets really busy, a second approach frequency 132.4 (Final) is activated. Later at night though, 125.7 handles all of these sectors, including KJFK Departure 135.9. I hope this helps...