1.) Pick a main ingredient to buy in bulk.
I go grocery shopping once a week, usually on Friday afternoons. But before I do that, I like to decide on one main ingredient to build all my meals for the upcoming week around (like chicken, for example), and buy enough of that item to last the whole week. Not only does this limit the amount of ingredients you'll need to buy for each meal, but it also makes planning your meals for the week a much easier task.
2.) Plan your weeknight meals ahead of time.
"Main ingredient" for the week: Chicken
Sunday: Chicken Bacon Ranch Pizza (easier than it sounds with pre-made pizza dough on hand!)
Monday: Chicken Scampi
Tuesday: Chicken fajitas
Wednesday: Salad and rice/quinoa with chicken
Thursday: Mac & Cheese plus any leftover chicken
3.) Shop consciously.
By having a plan and a list of groceries before your shopping trip, you'll avoid buying extra items that end up sitting in your fridge unused, taking up space.
Having a plan will also save you money in that regard. However, it's still important to be mindful of the price tag across different brands, stores, etc.
4.) Prep different items.
As I also mentioned in my post on navigating a shared kitchen, I like to prep different items ahead of time, usually on Sunday's or whenever I can before the week picks up: chopping all my vegetables and storing in individual bags, making a large batch of salad dressing for the week to keep in the fridge, etc. I highly recommend this to save time each night when making dinner.
Happy cooking, and be sure to stay tuned for the next Sum-It-Up Sunday on the 25th!