I've got 2 silver saxes, no lacquer. My wife has a silver flute.
You need to distinguish between silver and nickel plating and also whether the keys are silver plated or nickel silver (a lot of brass saxes have nickel silver keywork, not silver plated).
Nickel silver is pretty much the same stuff as 'silver' coins are made of, just needs a bit of metal polish every now and again. Avoid the abrasive polish. Same for nickel plate. Mostly you can clean by wiping it down after use with a soft micro fibre cloth.
Silver/silver plated saxes do tarnish, but it's really easy to keep under contol - just wipe thoroughly with a soft micro fibre cloth after use, and store in the case. Once every couple of months or so use silver cloth gently (my wife's never done this with her flute and it still has no tarnish after 12 years). If the tarnish builds up under/between the keys where you can't get at it, either use a silver cloth and blunt kebab sticks to push it in, or leave it until the next time the sax is disassembled for repair. I've takenthe keys off mine once to clean under/between them, cos it was too deep seated to leave (annoying me). Don't use the abrasive silver polishes - stick to non abrasive liquid polish or better a damp silver cloth - the liquid polishes get on the pads and it's difficult to remove.
If the sax is lacquered, just a soft cloth, maybe a bit of furniture polish.
Other suggestion (from cybersax.com, I've not tried it myself)) is to put special jewellers paper in the case, but I've not found any to try it with. Not heard of the activated charcoal trick before, but it may work - although for how long I don't know, as activated charcoal absorbs a lot of other things which'll reduce it's effectiveness quite quickly. You can buy it reasonably cheaply from pet shops which stock fish - it's used fo wate puifaction, and bulk packs are quite cheap, can't say the same for filte inserts, though.
Avoid rubber gloves when cleaning silver saxes, they contain a lot of sulphur.