Did you know that an average American household wastes $640 to $900 on food a year? A survey conducted in Washington has shown that at least 53 percent of households end up throwing away leftovers or food they haven't opened or eaten every month, according to the American Chemistry Council.

Needless wastages can be avoided if consumers learn to shop right and ditch bad grocery shopping habits. Here's how:

1. Always keep an inventory of what's in your pantry and fridge. This way, you'll have an idea of what items are still in your kitchen and avoid purchasing supplies you already have.

2. Always keep a grocery list. Having one cuts wastes both in time and money. Without a list, you'll either end up buying extras or forget to get the essentials. Select and download any of the grocery lists from Grocery Lists Org.

3. Never do the grocery shopping when you're hungry. You're bound to buy more food you don't really need on your cart. Worse, you'll end up buying unhealthy, high calorie food. "People should be more careful about their choices when food-deprived and possibly avoid choice situations when hungry by making choices while in less hungry states," researchers suggest in a study published on the JAMA Network.

4. Know which foods to buy in bulk and which foods to buy in smaller packages. Buy items in bulk when you know you'll use them for the next two months, such as spices, rice and grains, paper products or nuts. Don't buy items in bulk when they will spoil fast, such as fruits and vegetables. Also, don't buy snacks, chips and candies in bulk, as these will only promote unhealthy eating.  Always check for expiration dates even when you're buying in bulk.

5. Learn to change up the recipe and substitute ingredients. Everything can be "Googled" these days so if you have items in your pantry that have yet to be used, check online for recipes you can cook using these. Check out these healthy substitution recipes from Shape Magazine.