I have moved my 20g office tank 3 times in the last year (it's at home now even though they have assured me no more moves)
It's easy - just have some transport buckets (I use old salt buckets with lids). Take all your rock out first and put it in a bucket - cover with tank water. Then take some additional water and put it in another bucket and move all your inhabitants to that. Try to take as much clean tank water as you can. Then just dump the remaining water and sand into whatever disposal devise you are going to use.
Make sure you have lots of freshly mixed new salt water at your new location. Place the rock in the tank and stack it the way you like. As I take the rock out of the transport water I like to have a bucket of salt water to swish the rock around in and remove as much trapped gunk as I can. Once the rock is stacked then pour as much clean tank water out of the transport bucket as you can. I have noticed that during transport a bit of crap seems to come off the rock so try and not put that back into the tank. Then just add the remaining transport water with your corals and critters into the tank and top up with fresh water. If you are planning to add more sand then you should do that after you place the rock and maybe give it a day to settle. If you do this make sure that you have a small powerhead in the transport bucket with your critters in it.
Sorry for the long post - but that's how I do it.