I agree with BargainBinge, it's good to know what you have to work with.
If you are just starting out with menu planning, it might be a good idea sit down with your family to brainstorm what your favorite meals are. Some may really like spaghetti, others may enjoy the meatloaf. Some of your family members may like your cornbread recipe, but others may prefer rice. If you have picky eaters, this may be a way for them to feel like they have a voice in the dinner plan.
After you get about 2 weeks' worth of dinner plans, get out a piece of paper and write down all the ingredients you'll need to make each meal. This will help you with grocery lists.
I used this strategy when I was just starting out on my own with DH. It worked great. When we sat down to do our dinner plans, he told me that lima beans are his favorite veggie. Who'da thunk?? So I try to keep lima beans on the menu at least two or three times a month. Broccoli is my fave, so we eat that a few times each month as well.
Now I have a list of about 45 dinner ideas. That helps us keep the variety. Some of those ideas are soups, which we mostly eat during winter. Since I have a wide variety of meal possibilities, I can look at the store circulars and just "know" what to make with what's on sale. So if frozen spinach is on sale, I may stock up a bit, because we like spinach in our soups and sprinkled on pizza. Then, later, I can plan the weeks' menus around what I have on hand in my pantry, as BargainBinge does.