I live under the 22L approach course for Kennedy and practically all of my scanning is Kennedy Approach. Pretty much all of what Jason said is accurate however, with the wisdom of scanning these frequencies for the past five years I would just like to clarify a few things. First, the relevant frequencies for JFK Approach, starting with the most relevant are 125.7, 127.4, 132.4, 118.4 and in a distant fifth 134.35. On the departure side, 135.9 is the only real JFK departure frequency. As compared to the AirNav listing, 125.7 is a glaring omission, while 127.3 is LaGuardia approach and 126.8 is a Liberty departure sector.
To elaborate on the sectorization and frequencies:
125.7 is the base frequency for JFK app. and dep. It is the only frequency which is operational 24 hours a day. From roughly 11pm to 6am or 7am it does everything for JFK and also for nearby FRG. It handles all arrivals from all three fixes: ROBER, CAMRN and LENDY along with all departures. When traffic begins to pick up in the morning the workload is gradually divided up.
First, 135.9 begins to handle all departures.
Secondly, 127.4 enters the mix. How the approach workload is divided between 125.7 and 127.4 depends on the runway configuration:
1) When the 22's or 31's are in use 125.7 is the "final" sector (the sector that hands out approach clearances) and also handles ROBER arrivals from start to finish. 127.4 handles CAMRN and LENDY arrivals and hands them off to 125.7 for final vectoring.
2) When the 13's and 4's are in use 127.4 is the "final" sector and handles CAMRN arrivals from start to finish. 125.7 hands off ROBER and LENDY arrivals to 127.4.
When traffic becomes too much for 2 controllers to handle, 132.4 enters the mix acting as the "final" sector with 125.7 and 127.4 feeding the arrivals into it. Note that this is only from 1pm-9pm at most.
118.4 is rarely used but also has a variety of uses. Sometimes it simply subs in for one of the frequencies, taking over all its functions and following the same rules above. Other times it can even become a second "final" sector. This happens on a busy afternoon when the VOR 13's are in use with the VOR/DME 22L. In this case 132.4 would usually be the final freq for the 13's and 118.4 the final freq for 22L, although I have seen the opposite be true as well.
The only reason I included 134.35 on the list is because a handful of times in the last 5 years I've seen it take over for 125.7, once again performing all the same functions, just on another frequency.
If it were up to me, I would dedicate one feed to 125.7. In fact, my scanner usually stays locked on this frequency. It can get quiet during the afternoon/early evening with all the other frequencies going but there is always the Republic arrivals and departures to keep it interesting. Personally, some of the most exciting scanning is around 11pm and 5-6am when this frequency is working everything and there is still a moderate amount of traffic. It’s hard for anyone to get a word in. The best thing about this frequency is that it offers at the very least a little of everything and you'll almost never hear a controller without a pilot response, which is one of my pet peeves.
I suppose the ideal situation would be with 2 sites each with 2 receivers and each receiver dedicated to one frequency: 125.7, 127.4, 132.4 and 135.9. 118.4 could be tacked on to one of these but is probably not necessary, and don't even bother with 134.35. Keep in mind when pairing up frequencies that when not in use the controller is still broadcast on most of these frequencies.
Hope this helps, sorry if it's too much but I had to jump at the opportunity to put this seemingly useless knowledge I've acquired over the years to good use.