wing it all the time, pretty much. usually i have pasta/rice and bread and soup and veggies and fruits and cereal on hand, and if i need anything else i'll run down to the supermarket. i like grocery shopping so this works out fine for me.
I rarely plan. If i have an actual real arrangement for people to come round to eat i may make a rough mental shopping list and have a look at a few recipes (real or mental ones)... then i might shop...then i'll wing it.
"We knew he was someone who had a tragic flaw, that's where his greatness came from"