I like to know what is in each box so packed my own.
I used coloured paper (thanks kids) and cut them into large squares, each square was numbered for the box and I stuck a coloured square in the top corner of every side of the box so it could be seen from all angles, and one on top. I also had clear tape in a packing tape dispenser, made sealing boxes easy and putting the labels on easy.
So the dining room contents were in green boxes, kitchen was yellow. I also did exactly what Thinkle did and listed the contents of each box in a notebook that lived in my handbag so I didn't lose it (also where I wrote meter readings)
I listed stuff as to what item it came out of, so dining room would be the sideboard stuff, or lounge X storage unit or cupboard under the stairs. The thought being that if I knew where to find it in the last house, I could find it now.
I did separate kitchen items into used infrequently (orange boxes) so cake tins etc and then items to be unpacked immediately (red boxes) plates, bowls, mugs etc.
When we got keys for the new house, I stuck the coloured paper of each room over the door frame so the removers knew which room to put it in. That way I could be in the kitchen unpacking not having to tell them where to put stuff. Just because something came from Ds2's bedroom at the last house doesn't mean that is where I want it at the new house. I kept his room clear to decorate asap as he was 3 and I knew he would struggle so I decorated his room within 2 days of moving.
It is never to early to pack, although I like a long exchange to completion so we had 3 weeks! I definitely knew we were moving out.