Most meals we make are designed for leftovers. We're too busy, we generally like leftovers, and it's easier than avoiding carb landmines in takeout or restaurant food. So I guess that's a food prep technique that helps provide meals that are ready when we want them. Foods that reheat well (soups, stews, casseroles, anything that doesn't have to be served crisp or is all that delicate, like fish) predominate. If I do make fish, I'll use the cold leftovers on a salad or something to avoid reheating it.
Since there's just two of us, almost everything that makes more than two dinners and a lunch is frozen for some future date. Everything that goes into the freezer is labeled with what's inside, a quantity ("4 chicken drumsticks", "1 lb rhubarb") and when it went in so we can use it before it's too old. A freezer and a microwave with a good defrost function is a help, too, for those "Ooh -- gotta make something for dinner" days.
I'll store food in whatever's hanging around. We have lots of yogurt/sour cream containers that are good for holding chili and soups in not-enormous portions. Leftover plastic disposable containers (like the rigid Ziploc kind) are good for vegetable leftovers or a couple of pork chops. I have some glass containers but tbf they're heavy and they do break. On the other hand I don't put most of our plastic containers in the microwave to reheat unless they're designed for that.
We also tend to keep some stuff in the house for really quick meals. I've taken to those egglife egg white wraps. A couple of those, a little cheese, some protein (like ham or turkey or a leftover burger), some salad greens (always in the house), and a condiment are a good meal, quick, easy, filling, and keto-friendly.
I'll see if I remember more ideas as other people post.