Hey Hot...I started out with brand new sand--I didn't want to stir up my old sand--that can cause a LOT of die off and a cycle. With my live rock, I didn't have to worry about a cycle...I did the following to do the transfer:
The night before the transfer, I mixed about 35 gallons of brand new saltwater with a heater, a powerhead and some buffer.
1: Take out inhabitants and water from 12g Nano Cube--put in rubbermaid containers with heater and powerhead...and drip acclimate with brand new saltwater (so when the tank is ready I can just stick everybody in there)
2: Take out Nano Cube from desk
3: Put the foam on the desk (this supports my tank--to support it in case it isn't even--less chances of tank cracking due to pressure points.
4: Put the 20g in front of sump, hook up powerheads and hook up the piping.
5: Fill with water.
6: Fill with sand.
7: Wait until sand settles a little, then put in rocks and inhabitants.
Keep in mind, it's different for me...my rock came from established water--and I didn't even toss my old water out, I just mixed it in with the new one.
When starting a brand new tank though...let it cycle, stick a cube of mysis or some shrimp in there to rot to generate ammonia--always start with something live (either rock or sand--or a little cup of live sand to seed--keep in mind, the less "live" things you have, the longer the cycle will take).
Then add your cleaning crew--you will have an algae bloom by now, which is all normal...diatoms will go crazy and probably some cyano and hairy algae. Make sure your cleaning crew can adequately keep your tank clean, then add your fish (I always recommend fish first prior to corals--). Fish have THE MOST bioload of anything you can put in your tank, if your tank can handle fish--you're good to go with the corals.