I've never worked out a perfect way to do food shopping.

There seems to be a choice between

1) Being ridiculously organised and planning every meal precisely in advance
2) Eating lots of frozen/tinned food
3) Wasting lots of food
4) Being a genius at making meals out of unlikely combinations of ingredients (or more often lack of ingredients)

I suppose in practice I end up doing a mixture of all four of these but I can't help thinking that I'm going wrong somewhere.

I've never worked out a perfect way to do food shopping.

You've clearly never been ruined by a Mathematics degree. :)

Just two mathematics degrees - they obviously cancel eachother out :-)