What strikes my fancy when I feel like having "X". I have a good general knowledge of what's in my freezer; so I'll take some chicken or steak tips out, and then go searching.
Or I bought a new condiment or marinade and want to try it out.
Or seasonal. Stews, long braises - they end in March or so, and start back up in October when the weather cools.
And I'll add that I'm just cooking for me. So I can change my mind at the drop of a hat without pissing anyone else off. :-)
I need to cook vegetarian, since Mrs. O requires it nowadays, and that fact has forced me to find or invent dishes that satisfy both of us while providing the necessary amount of protein etcetera. Some of our new favorites are of the kind that let me add meat of some sort to my portion; I keep closeable bags of shrimp and fish in the freezer, country ham and bacon in the meat drawer. When she goes out for the evening - she gets together with some old school chums most Thursdays - or when she's out of town for some reason, I might try some carnivore dish I've been wondering about or just have a steak or lamb chop.
I shop almost every day, since the fridge stays pretty well crowded and there's not much pantry space here. I did buy a smallish chest freezer which lives out in the garage, and am getting into the habit of buying several bags or packages of frozen items at a time. It also comes in really handy when I want to make a pot of something Mrs. O won't eat, like chili, and I'll freeze the leftovers in as many two-cup containers as they need.
The main criteria in my house are
1) What do I have time to cook (insane hours)
2) What are the highest-quality items that I can afford within my grocery budget
3) What fits my DH's diet guidelines (very low carb)
The season affects it too. I made a potroast on Tuesday night, something I hadn't done since...April? I think?
This is where meal planning comes in. Each week I look first at what I have that I want to use, then I look at the circular to see what is on sale (online we don't get the paper). Then I choose my meals from the manyany recipes I have in various formats. Sometimes I look at recipes first and do the process backwards. At one point I was making something new almost every night.
I am not a slave to a recipe any longer depending in what I am doing.
Last night I made Pakistani Goat with potatoes and ginger masoor dal.
Tonight is probably baked egg rolls.
ETA: I shop once a week and so when I get home all my ingredients are there. An I take out anything that needs to thaw and put it in the fridge the night before or two if it is large.
The main thing is it has to be something both of us may like. That means, among other things, no cream soups and not many vegetarian offerings. She won't eat the former and I'm unfulfilled by the latter. Also, bland foods are pretty much non-starters. We both love the heat and the spice. The Khantessa doesn't care much for Thai or Chinese, so those are pretty much out of bounds. And neither of us eat shellfish. If a recipe meets all of those requirements, it will fall under consideration.
And like sedimental, the complex and/or labor-intensive dishes are reserved for Saturdays and Sundays. On weeknights we cook quicker, easier recipes.
Ain't that the truth!
I go in "phases". Usually, I try to pick something challenging and interesting that I haven't made before for "weekend cooking". I have more time and can relax and have fun with something more labor intensive. I look forward to relaxing in the kitchen with some big "project" on weekends :)
For weekday cooking, I vary soooo much and often try different things out of my own ethnic comfort zone. I really like East Indian and Vietnamese foods...maybe once or twice per week I try a new recipe out in one of those cuisines. Then a creative soup/salad or sandwich "bistro night" one night, maybe a crockpot meal (soup, chili, pulled pork type thing) on a night where I know I will be late. I peruse recipes with those types of meals in mind.
Now that I put this in writing, I guess my choices are more about how much time I have to devote to dinner as much as trying out new recipes.