25L? You will be as bored as a rat...
Landing traffic usually takes 25L, except the cargo's (25R) and several Schengen-flights (going to Pier A).
25R gets all the rest (more traffic in general but small planes, aka CRJ's, B737's,...). The few widebodies we have here will have landed already before the Helvetic flight arrives, and before you will reach the spot.
Going to 25L: impossible by foot, you will have to take a taxi or hire a car. It will certainly take you one hour to walk (probably even more).
From the other side, you can always spot the departures. All traffic normally takes off from 25R (unless the winds turn of course).
From the terminal: you go outside, and walk down the road, till you are under a big bridge. You will see a few hangars, and the DHL planes on your right side. Enter that road, follow, and you will see a bridge.
From there you can get shots like this:
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Photo © Fabrice Sanchez
This is a picture of the DHL area I was talking about, + a bizjet at Abelag (on the left side of DHL):
You can always continue to the spot at Brucargo: when you are at the bridge where the UA
B763 shot was taken, you have to follow that bridge and turn right downstairs. Follow that street for about 100 metres till you have a road going upstairs. The aircrafts will fly over you. Continue and you will have this view:
Don't forget to bring some warm clothes with you...