Before they come, you need to pack certain things and keep them separate - either in your case it clearly labelled DO NOT PACK.
Personal documents, eg passport, insurance.
Personally precious/valuable items, eg jewellery, loose photos.
24h of stuff in case of delay, eg clothes, toiletries, medicines, bottle sterilising gear etc.
House cleaning kit, eg vacuum cleaner, wipes, etc, as you may want to clean the new place before you unpack. I would include kettle, a couple of mugs, and the necessaries for making tea.
The packers should label each box with the room in which they packed it. Either give them a plan of the new place, indicating where the contents of each room should go, or stand by the front door telling them as they bring each box into the new place.
They will literally pack everything. We tried to prepare for them and cleared out rubbish, but forgot to empty one wastepaper bin. They packed it! Carefully upright so that nothing fell out 😆