I live alone and am very regimented in the foods I put into my body. I go to 4 places. Whole foods, Wegmans (local awesome grocery store chain in PA), various farmer's markets, and on occasion Trader Joes. I'm a firm believer in the quality of the food you eat aids in one's quality of life. I primarily buy perishable items. Food is my 2nd largest fixed expense a month on average after housing. (caveat, employer pays for cell phone & gas. thus some expenses others may have are 0 for me & allow more put towards food).
Shopping at higher end grocery chains can get quite expensive. Thus, I routinely stock up on vegetables from the less expensive farmer's market for salads/cooking during the week. I purchase onions, baby spinach, carrots, celery, apples, and an assortment of other goodies for a week to two weeks. I keep many of them in the fridge and cook the items more likely to spoil on Sundays to ensure freshness during the week.
For proteins, I eat chicken, fish, and grass fed beef. That's it. I try to get the highest quality items. I freeze them when on sale (which is rare for quality protein). Sometimes I save by purchasing from a local butcher, but it's easier to buy from a grocery store. There is a cow share in my area, but I haven't found enough people willing to buy in.
Overall, I track every $$$ and my food routinely comes in around $250-300 per month. I pack my lunches, snacks, and dinners every day. Thus, my restaurant, takeout, & occasional fast food consumption is less than $50 per month. By cooking, I keep a healthy diet and
I take Saturday to plan out my meals for the week. I shop either Saturday afternoon or Sunday morning. I cook for 1 hr tops on Sunday. Sometimes I'll cook half on Sunday & the other half on Wednesday night. Crockpot is a must, especially for the beef. It saves time and energy. Overall, it's like working out. Set a schedule, commit to it, and automate as much as possible.