We did a HUGE declutter when we started showing our house. We packed up everything we could stand to live without indefinitely and either sold it, gave it away, trashed it or put it in a rental storage unit.
I was amazed at how much more liveable the place was without all our junk around! It made me want to stay! Well, maybe not stay THERE, but you get my point.
So the move happened in 2 phases: the U-haul of furniture/critical stuff, then later another u-haul for the storage stuff.
I have to say, I thought I was pretty organized, but the move was a total fiasco. Timing was crucial, because we had to close on our old house before we could sign on the new one, and the truck had to be loaded/unloaded within a limited time. It turned out the truck was too small, so the night before the new owner's 7 am walk-through, we're calling everybody we know with a pickup, station wagon, hatchback, whatever! OMG it hurts to think about it even now, 18 mos later. If I had it to do over again, I would definitely hire movers. Oh, and our new house was just 15 minutes from the old one, so it wasn't even a long distance move.
Not that your experience will be like mine, of course!
The one thing we really did right was getting rid of everything that we didn't have a foreseeable use for. For us, the biggest category was books, many of which were purchased second hand and were falling to dust. There was also a fair amount of obsolete computer stuff which was difficult to dispose of responsibly (which is why people gave it to us).