A really 'good' place doesn't really exist by my knowledge. However, if you are on foot and mainly go for numbers the east side is doable. Just go down to the bike trail from the terminal (watch for little signs like this near some emergency exit doors in the departure hall) and walk a little to the south. You have no views to the aprons, taxiways or runways from here, but can catch everything in the air. If it is a westerly wind you can catch arrivals (and may even be able to take a shot or two), if it is easterly wind you catch departures. In that case pictures are difficult, but you can read everything with ease.
If you are flying easyJet, go through security early and enjoy the views from the terminal. Especially the 'satellite' gates are good (don't know the gate numbers, but you'll find it).
Charlwood side is where I now and again see people snapping pictures, but it definitely depends on wind direction. Horley side (spot no4 on the map) is a spot where I myself wouldn't stand all day because of traffic over there. Don't know if it still tolerated by police.
If you have a car available then Charlwood is easily reachable. Parking your car near the spotting location is not that easy. Be prepared for a good walk from Charlwood village.
I dont know if you are into photo's or regi's but have a look at this site. http://www.plane-spotting-hotels.com/in ... g-gatwick/
There should be a new great hotel for viewing at Gatwick! I'm going to try it in July.
