There are three rules I stick to when buying vegetables and fruits, which determines what I will be cooking that week.
(1) Buy in season. The produce tastes better, is cheaper, and better for the environment. Think about how many resources it takes to grow something out of season.
(2) Buy locally. Now this can mean buying at a farmer’s market, which is great and hugely encouraged. However, farmer’s markets can sometimes be very expensive (unfortunately, this seems to be the case with my favorite market around here). So, look for a grocery store that buys local. I live in Colorado and the main chain, King Soopers, is very much into that. There are other store options as well. Anything with “farmers market” in the store name usually strives to buy close to home. Sprouts and Sunflower are two places I frequent. Their produce isn’t flown from across the Pacific and it is very reasonably priced, especially when it is in season.
(3) Buy fresh. There is only one vegetable I buy in a can and that is tomatoes. I buy canned tomatoes, tomato paste, and tomato sauce for a few reasons. First of all, when tomatoes are on sale they are still more expensive than when they are in the can. Second of all, it is quite a process to prepare tomatoes for marinara sauce, chile, etc. And these are the only times I use canned tomatoes. I still buy fresh tomatoes and use them whenever I can. When and if I ever make more money, canned tomatoes will be the first to go.