I just moved from a 135 to a 265, and here is what I learned:
1) Get EVERYTHING ready in the new tank FIRST.... Get the water up to the same temp and salinity as the original tank. Get the water circulating, and the lights ready to go....
2) Move SOME of the LR (live rock...) from the orig tank to the new tank, (or buy some new LR and supplement each) and then wait a few days. Siphon off whatever water level increase from your sump back to the original tank.
3) Have someone help you (when you are ready to move) and get a peice of egg crate (white plastic stuff) and cut it to the depth and width of the tank. Use this as a "divider" to help you coral (spelling?) the livestock as you try to catch them.
3.a) Move the rock first (duh) in order to give you netting room. Be prepared to siphon water back to the original tank as the water level in the new tank increases.
3.b) Have enough bags on hand to "float" the livestock when moving from tank to tank.
3.c) Have a MESS of towels.. it doesn't matter how neat you think you are going to be, you WILL make a mess.
Make margaritas, and enjoy the new tank!