How much food to you keep in the house?

I think you have to strike a balance between being organised and being spontaneous.
When the children were at home I planned a whole week's meals, shopped once a week and stuck to the plan. I would make double quantities of anything freezable so that some nights it would be just a matter of defrosting something and doing fresh vegetables or salad.
Now though with just two of us, I only plan 2 or 3 days ahead and if we want to go out on the spur of the moment we can., without wasting anything.
One thing I have found in the year since retiring is that we seem to have gone away a lot and I am constantly thinking that I'd better not buy something because it won't get used up in time before the next jaunt.
I still do a weekly 'inventory' and replace any of the staples, rice, pasta, tinned tomatoes etc that are running low. I haven't enough space to keep several packets of stuff.

For many years, even when I was with exdh, I have always done a meal plan for the week. It is NOT set in stone, but that, coupled with doing a sort of feezer inventory from time to time, really helps. Also try to bulk cook where possible, and freeze any left overs. (Have just put the remains of yesterdays beef casserole into the freezer, only a portion for one, but hey!)

It means that the shopping list is based on the meals, plus any other things that we need, and things that will actually make meals,but of course if I see bargains, (esp. reduced to sell stuff that can be frozen) I grab them.

Store cupboard wise, always a fair amount of pasta in different shapes, tinned chopped tomatoes, tinned ratatoullie (very useful, helps to bulk up a casserole or stew, can make a great pasta sauce with a few added ingredients, or the basis of a vegetable curry), part baked bread.

A couple of years ago we couldn't get out of the village due to snow. For the first few days the village shop managed to supply most of what we needed, but then they ran low as the suppliers couldn't get to them! I became very good at stretching things, a lonely steak in the freezer was sliced up and turned into a sort of mock stroganof, the odd portion of smoked fish and the tail end of a bag of prawns became a fish soup, served with one of the part baked baguettes from the cupboard.

Luckily I tend to keep a good stock of cat food, I might easily have had a mutiny on my hands!

With my plan to, hopefully, retire next year I'm trying to get organised with food. Over the past few years I've cleared out food that my son has left here, both freezer and larder stuff. And the S.O. tends to do the shopping, so I find things in my freezer that I didn't know I had. I want to get my life organised now that the kids seems to have actually really left home properly [apart from leaving rooms full of clothes, stereo equipment, guitars..I could go on but y'get'm'drift]. I'm always curious [well, nosey] as to what other people eat. I'll often have porridge when I get back from work and then just an omellette or salad later. Throw in the odd banana and apple and that's me done for the day.

Same here, although I do tend to get carried away after I've defrosted the freezer and go mad filling it - only to end up when it comes to defrosting time again having to throw away things I've forgotten about...
This Christmas I'm determined (yet again) not to over-buy. [fat chance emoticon]

Same as yours jessbut over the last year or so as money has become increasingly tighter,I tend to shop every few days,and write a list of what is needed but like to keep a few store cupboard essentials and be able to knock a meal in an emergency or in case of a visitor or twoxx