its hard to figure out what to get if you dont know how to make anything. you mostly try to cook by recipe. the problem is you're never going to the supermarket with a tome of them. as you stand amidst the overwhelming aisles of produce, it is hard to not be a deer in headlights.
the first step is to not be afraid that you wont know what to do with what you buy. let's assume you have no idea what to get. well, what do you like to eat? by that, i dont mean particular dishes, but rather, ingredients. for example, i like chicken, and being asian, i prefer dark meat. i always get a bunch of thighs. be sure to store them in meal sizes (two or three pieces) in freezer bags and store them for later. do this for your meats, vegetables and carbs. unfortunately , vegetables and certain fresh carbs (breads, fresh pasta, unfrozen bagels, etc) have a shorter shelf life than meats, so you may not want to buy as much and make another trip to the grocery store.
once you get all that stuff, then you can start thinking about what to cook. to help, there are a lot of sites and chefs that specialize in simple meals. after you've done this a few times, you can start making your own creations. later i will drop some wisdom on general cooking techniques that works for everything. it'll make sure you dont make bland or burnt food.
right now i gotta goto the supermarket. i'll let you know what i come back with.