You could very well be thinking "duh", but I wanted to make this point very clear. You do NOT need to use a coupon for items that you could have a coupon for (most of you time you won't have coupons for meat, milk, or produce...although they do come around every once in awhile!).
All of us have things for which we're brand-loyal. For those, make sure you're always seeking out the coupons for that brand. But re-evaluate every once in awhile. Give the generic or the other brand a shot if it'll be cheaper. If you still don't like it, that's fine.
But for things that you're not brand-loyal to, check the unit price on everything. Take your coupons with you, so you're prepared, but it is absolutely okay to buy the generic (or cheaper brand name) if it's still cheaper than the brand you have a coupon for. I see way too many people in the store, for instance, buying something for $3 after coupon when they could get it for $2 without a coupon if they just bought a different brand.
Just don't get sucked into the common belief that if you're using a coupon, you're getting a deal!