Okay, I appreciate this is a fairly random and somewhat "You have far too much time on your hands" type question, but how do you pack your supermarket shopping (if you shop in such places, some people may not do so, granted)?
This question arose out of a discussion come argument between me and my flatmate recently; he used to work for Tesco (a British supermarket, see links below) and thus feels superior to me in this respect. I'm just going on experience.
Personally, I group things into categories; Frozen foods, Chilled foods, Ambient foods, and amongst those, into groups, such as carbonated drinks, tinned items, etc, although I try to balance the weight across multiple bags (I don't drive, so this is important... walking leaning to one side is not good for your health!).
I also have some obsessions, i.e. keeping cleaning products entirely separate from food products (this may just appear to be common sense to some, but many people believe i'm just going OTT with it), having chilled packaged and deli counter meets double-wrapped (using those transparent wrappers they have for this purpose at the checkouts), etc.
This is not an environmental perspective, re: the use of plastic carrier bags (I generally use re-usable "Bag for life" type versions anyway), merely the actual packing process...
"Bag for life" concept: http://en.wikipedia.org/wiki/Bag_for_life