When it comes to buying off the shelf items, it does pay to read labels. Now I'm not saying to go over board and scrutinize the item to the Nth degree, but there are some considerations to keep in mind. If you are looking at a jar or can of spaghetti sauce and they list high fructose corn syrup anywhere in the 1st 4-5 ingredits, put it back onthe shelf and keep looking. HFCS is used in a lot of products because it is a cheap filler to try an fool your taste buds into thinking you are getting what you are paying for and the company can skimp on other ingredients. A little bit of sugar does have it's place in spaghetti sauce. I use a teaspoon or so in mine to cut the acid from the tomatos, that is a cooking tip I learned growing up. You can easily get away with not adding any if that is your preference. I go either way.
HFCS has it's place on the table as a sweetner for many items meant to be sweet (tho it is being used to sweeten items I think they should stop messing with. Coca Cola made with cane sugar is far superior then Coke with HFCS), but it is being used to adulterate too many items on the store shelves simply so the company can skimp on the other ingredients.
The other consideration for reading labels is if you have food allergies. Some folk are either allergic or intolerant of wheat, and it is amazing where that can hide. So, if you do have any kind of allergies or intolerances, learn the different ways they can hide in your foods so you can recognize them.
In general, if the ingredient label reads like a chemistry text, you may want to reconsider the item you are buying and see if there is something comparable with less science and more actual food (tho there are times when the processed food stuff is what hits the spot, the trick is not to use it for your sole survival). The key is moderation. Hamburger Helper can be yummy stuff, but eating it every meal in the long run is not good for you.