If you want to take your cooking up a notch, check out Cook's Illustrated magazine and Cook's Illustrated Cookbooks (some are available at Costco).
Cook's Illustrated runs a test kitchen where they literally develop and test recipes dozens of times to find the perfect/foolproof recipe. Cooking/baking is nothing less than CHEMISTRY, so a different amount of an ingredient or a different ingredient altogether really can make a difference. For example, they will tell you why in a given recipe butter works better than margarine, or why changing the temperature will give you better results.
Their recipes are not for the busy Mom that gets home from work at 6:00 and needs dinner on the table by 6:30.
But if you have some time, or on a weekend you have the time to prepare a special meal, you can't go wrong with their recipes.
At the risk of being immodest, I will say that my cooking skills have improved dramatically, and the gourmet meals I prepare rival some very fine restaurants I have visited. The thing is though....it isn't ROCKET SCIENCE...with a little time and experience anyone can do this, and do it well.
Here is a cardinal rule: Do not substitute canned for fresh, or dried spices for fresh herbs. If you make an effort to use only fresh ingredients, I guarantee you will taste a difference.