Clean and organize. Laundry, dishes, tools and other items pack and move easier when they're not a mess.
Purge! Go through and pull stuff that you can trash, give away or donate. Remove these items before the packers arrive, or gather it all into one pile and clearly mark it "DO NOT MOVE!"
Pull items that you'll move yourself. These normally include medicines/toiletries, enough clothing for the move duration, personal items (electronics/chargers/books), work stuff, jewelry and hazardous items that packers and movers won't touch. Pack these things ahead of time, or clearly mark them.
Organize and label rooms. Have all your master bathroom items in your master bathroom, for example, and use signs to mark every room so the packers can mark boxes accordingly. If a large item will switch rooms in the new house, just mark it with its own label.
Back it up. Use portable hard drives (that you keep with you) or cloud storage to back up any important computers, tablets, etc.
Mark high-value items as such. Whether it’s a truly valuable vintage record player, or an old music box that has more sentimental value than collector value, this tells packers and movers to take extra care with these items.
De-clutter. Packing moves faster if the team has surfaces to work on (tables, countertops, etc.) that are clean and open.
Walk the walk & talk the talk. Tell the packing team your expectations and make sure you're available if they have questions. Walk through your home before and after the packing job and make sure it's all done to your satisfaction.
Prepare for a snack attack. Everyone loves snacks. Have some cold water or lemonade and some cookies or granola bars available to the packing team. Warm chocolate chip cookies earn extra points.