Allocate a spare room or end of a room and start now, pack up stuff that you wan't need for now like summer clothes, holiday stuff, garden toys, spare bedding and towels.
Label the box with a room name and a brief run down on contents may be a pain but it makes it so much easier. It means there is less rush to unpack, as you will be able to find what you need easier, rather than emptying every box to find one thing.
Don't pack junk, decide now
do you need it,
do you love it,
do you use it,
or does it fit.
Be ruthless now no point in paying to pack and transport rubbish.
On the day have sheets of plastic or tarpulin to hand to cover boxes and furniture if heavy rain when carrying in the house. Old towels to dry things put down on floors etc. Consider one of those plastic runners you can but by the length to cover downstairs carpets.
Cheack list for sorting out utilities etc are very helpful as on the day your brain will be mush. Be very clear about arrangments for everybody else, even if it means writing down a time table on a big sheet and sticking it on a door.
Agree make up a vitals box and keep to hand take it in your car, include kettle and cuppa stuff, favorite toys, cutlery for eating takeaway, lists and phonenumbers, firstaid kit.
Also consider sleeping arangements for the first night, keep bedding in mind and night clothes etc.