The general consensus seems to be that the freezer is a bad place to store beans/grounds, the fridge isn't great either (because it's too humid), so your cupboard is probably best since it's dark and coolish and usually not too humid. Since your biggest concern should be exposure to air (since oxygen is coffee's #1 enemy), we actually turn to our trusty Mason jar to store beans and grounds, since we know a Mason jar's seal is as airtight as they come. But some folks actually say keeping it in the bag is best, while others recommend vacuum canisters like this one by our friends at Fellow.