i think you can buy a starter kit of kritters and such that will seed your sand and live rock, its not alot but its something.
alot of old school methods were to either use an old panel filter from someones established tank or to take a few cup fulls of their sand to kick start the colony.
i'm starting a new tank soon, been waiting for a top brace for a 72g from my LFS for 4 months now( yeah i know they better give it to me for free) which i will be using dry rock on, a few weeks before i put fish in i will moves all my water and rocks to a smaller temp tank for a few weeks and the rest of the water and sand will be going in the new system to seed that deep sand bed and the dry rock, which is mostly cycled now sitting in a rubbermaid bin, i just add skimmate every few days to feed the bacteia colony