We don't plan too much. Steve does a shop for fresh meat, fruit & veg at the weekends from our butcher and green grocer, and then the other stuff from either Sainsburys or Morrisons. (We rarely ever buy lots of groceries at one time unless we are going to be entertaining or having guests stay with us for a period of time.)
Whatever he picks up at the butcher and/or green grocer usually sees us through to at least Monday, and often more than that -- plus we usually have fruit & veg enough for the week. We'll pick up odds & ends through the week as needed, or go to the city market (on our lunch breaks) which is amazing for fresh meat, fish, produce, etc (as well as a smorgasbord of anything/everything -- cheap groceries, electronics, clothing, textiles, wigs...)
When I cook (the days I'm off or taking a turn at mid-week cooking), I cook BIG meals (like chili, spaghetti sauce, soup, stew, etc) where some gets either used as leftovers on a subsequent day, or frozen & used as convenience meals later on. Recently, we've had so much of this stuff in the freezer, I've not had to cook at all!
I cooked a lot more when I wasn't working. But ever since I've been working, particularly the job I have now -- Steve knows how stressed & tired the job makes me on the days I am at work, so he tends to take over in the kitchen (and the washing up too!). He likes his job a lot & he likes to cook -- so this has been a happy arrangement for us.
Our cupboard is always well stocked with staple ingredients, spices & seasonings & things to bake with. I guess we do plan to the extent that we both sometimes cook to recipes we want to make -- but it's all on a very ad hoc basis for the most part.
We like leftovers! I'm not crazy about having just plainy-plain leftover chicken, so I usually recycle leftover bits of chicken into a new dish.