Put into plastic bottles (not too full) or other containers and put into freezer.

It will stay fresh (although, depending on how you stored it, might take on the freezer taste), will help your other frozen goods in case of power outages.

And tap water's cheap enough so you can just toss some out if you need more room in your freezer.

I think the main points is to use really clean vessels and keep them out of direct sunlight.

I wouldn't use salt for water storage, unless you face some circumstances where you need large amounts of salt water quickly. It might not be fit for drinking.

-jh