Something airtight to keep the insects out. Read a story about a fellow walking into his grain storage room and seeing it alive with moths
You can store grain in the fridge/freezer - I havent' done this but have read recommendations from people who swear by it. I imagine you just need to be sure that no moisture gets in. I've also read about people advocating purging with Co2 whenever you remove any grain from a container (kill any bugs and prevent oxidation).
In general whole grain keeps much better than crushed. eg. a chap in Newcastle has hundreds of kg. of malted grain stored as is in sacks for at least a year with no ill effects. When he opens a new sack he just transfers the contents to a 25 litre container.
Interesting message here on grain going stale and why this happens and why it's more a problem with crushed grain.
http://groups.yahoo.com/group/CraftBrewing...ng/message/9385
However crushed grain should be ok for some weeks at least if stored in a dry, cool airtight container.
cheers
reg