Pack a suitcase as if you were going away for a long weekend.
Pack a box of all important paperwork (including related to move) as well as things like passports etc
Pack a box of food essentials (as if you were camping - coffee, teabags, sugar etc... including snacks for movers and you)
Pack a box (eg shoe-box) of essential tools (we had a special thing to take apart / put together bunk bed, which movers didn't have). Plus we needed to pull out some fitted furniture to get our furniture in. Plus we had to pull up the downstairs loo carpet, that hadn't been changed for about 20 years, and made the house smell like a public toilet. I couldn't sleep for a night with it in the house!
Everything above went in car with us.
I packed things like contents of bathroom cabinet into shoe-boxes, as in previous move the packers had chucked all these tiny things into the bottom of a large box, and thrown in the loo brush on top. Lovely.
Depends how much time you have...
Oh, and keep out lots of marker pens to mark up the boxes. In two recent moves the packers kept packing the pens!