I was in my local supermarket the other day and watched a lady pack her bags at the supermarket and was amazed. I get all flustered, and usually have 2 small children with me so anything goes in any bag (I do try and put the heavier/bigger stuff on first), but it's still a bit of a nightmare and I have to sort out everything again when I get home.
Anyway, what she did was put everything on the conveyor belt, got out her canvas type reusable bags and opened them all in her trolley. As soon as the girl had scanned it she put it in whatever bag she wanted.
I have done it today and it was so stress-free. I had bags for fridge food, freezer, cupboard, bathroom, non-food etc. I must say, you will need to go to a checkout that has someone before you because you need to get everything on and your bags open before before she starts scanning.
Most people could have said that in a few sentances - sorry!