Why run out to buy an ingredient you forgot at the grocery store, especially if you only need a little bit? Even if I write a grocery list, I tend to miss things and end up discovering my mistake mid-recipe, when dashing out to the grocery store would be a) impractical and b) really annoying.

So what do I do? After I finish grumbling to myself, I whip out the best substitution I can find in my fridge, especially if I only need a little bit. It turns out that you can avoid a dinner disaster with a little ingenuity-and hey! some of these substitutions may even make dinner better. Here are some common ingredients you probably do have in your kitchen that you can use as a substitute in a pinch.

1. Don't Have Ricotta? Substitute Cottage Cheese. Not only is cottage cheese great for dipping your veggies into, it makes a great ricotta substitute. So next time you're making lasagna, consider substituting cottage cheese instead of ricotta cheese if you're in a pinch. Although not quite as creamy, cottage cheese has a similar mild taste, fewer calories and less fat than ricotta cheese (81 calories and 1 gram of fat for low-fat cottage cheese vs. part-skim ricotta, which has 171 calories and 10 grams of fat).

2. No Sour Cream? Substitute Low-fat Plain Yogurt. Although I would hesitate to eat my granola with sour cream in the morning, this substitution works great the other way around. Next time you need to top your taco with something creamy and you're out of sour cream, try plain yogurt instead. In small amounts, it offers the same delicious tang and creaminess that sour cream does. But be wary when cooking with this substitute-yogurt breaks easily, so if heat is involved you're better off sticking with the original. If you're baking, try these 7 no-fail baking substitutions that won't ruin your recipe.

3. No Half-and-Half? Substitute 1/2 cup reduced-fat milk and 3/4 teaspoon melted butter or 1/2 cup nonfat (or low-fat) evaporated milk. If you've got low-fat dairy and butter in your fridge, then you've got half-and-half (well, almost). Adding butter adds fat right back into low-fat dairy products if your recipe is begging for a little richness. Or dust off that can of low-fat evaporated milk for the pumpkin pie you never made last year. Since it's concentrated, you'll get a similar result to half-and-half.

4. No Ketchup? Substitute 1 cup tomato sauce, 1/2 cup sugar, 2 tablespoons white vinegar. Who wants to eat French fries without ketchup? No one. But it's not worth a dash out the door if you've run out. Just mix tomato sauce, sugar and vinegar together and you've got ketchup. If you're feeling brave, you can even add spices for your own personal twist.

5. No Sesame Oil? Substitute 1/2 teaspoon canola oil and 1 1/2 teaspoons sesame seeds for sesame oil. There's reallyno reason to have 8 million bottles of oil sitting around your cabinets. Canola oil makes a great stand-in for olive oil (although it's less flavorful) and it carries the flavor of sesame seeds nicely. So don't fret if you don't want to add to your growing collection of bottles of which you use only a tablespoon once every other year. Try tossing sesame seeds in canola oil instead.

6. No Hot Sauce? Substitute 1/2-3/4 teaspoon cayenne plus vinegar. If you're like me, you have hot sauces from every corner of the globe in your fridge. But for people who don't love heat, investing in a giant bottle of hot sauce may seem like a waste. So just having a couple teaspoons of cayenne pepper on hand to mix with vinegar does the trick if you're in need of some extra zing.