Unless you are ordering a year's worth of juice at a time, no special storage is required other than a cool, dark space like Ricanrod suggested.
If you are planning to really stock up, it's safe to assume that the basic ingredients used in ejuice (PG, VG, Nicotine) have an average shelf-life of between a year to 18 months depending on when the base ingredients were manufactured.
While some ejuice vendors will state between 24-27 months for their product, I've purchased pure PG from US distributors that had an expiration date on the bottle that was within 18 months, and the lab certifications I've received on the Nicotine I've purchased state 12 months when stored properly.
To get the longest possible shelf-life, store ejuice in opaque containers (or out of the light), with as little air as possible to prevent oxidation and bacteria, and keep in the freezer until ready to be thawed and remixed before use.
To answer mohawkx question, some people have reported loss of flavor, flavor and/or color changes, as well as a rancid taste after refrigerating ejuice for a long period of time. This could be due to reactions by the extra, unknown ingredients used in "store bought" juice, due to bacterial growth, or due to some other factor.
At this point we don't have a definitive answer, so most advice errs on the side of caution.
Of course, YMMV, and if in doubt, contact your ejuice vendor and ask for their recommendations on storage for their particular product.