I've seen people put a little rice in a salt shaker-I guess to keep it from clumping. Not sure if that means anything to us preppers(?)
My father ran a charter fishing boat since 1971 and this rice trick is a big thing in a very humid environment.
As everyone has already said salt and sugar are the easiest storage item. But don't use o2 absorbers like some have mentioned.
Airtight( or more specific, ant tight) container sugar will last 15+ years and if chiseled and regranuarilized pretty much for your lifetime. Salt can be stored the same way pretty much forever, you can pass it down to your grandkids.
If you have the room I would just keep storing salt when you think of it. The cheap bucket with cheap lid from walmart and you are good to go. Or my last 25 bag (they only cost 4.40 at smart and final or Costco) I put in 2 liter bottles. It may be worth something some day, if not your family will never have to worry about salt.