Keep a clean fridge and well-organized pantry. It helps if you can actually see everything in your fridge and freezer without having to pull things out or push things aside. Chances are, if you can't see it, it's going to spoil before you remember to use it. Also, knowing what you have on hand can prevent running out at an inopportune time or picking up an unneeded quart of milk.
Prepare to prepare. If using a recipe, read it several times before starting in. Make sure all of your ingredients are prepared (measured, chopped, etc.) according to the list of ingredients before starting. If a recipe calls for chopped onion, don’t plan to chop it after you've begun. Have the required tools and equipment ready as well.
Take a cooking class. Improving even basic cooking techniques can help you understand how and why certain recipes work and is key to learning to create custom recipes and knowing if, when and how to substitute properly. The money spent on a good class can pay for itself in improved kitchen economy, efficiency and accuracy.
When rehydrating dried tomatoes or mushrooms, save the soaking liquid. If you can, substitute it for water in the recipe in which you are using them, or save and use in soups and stews, or use to boil dried pasta or make rice.
If you need to soften butter in a hurry, place the wrapped stick in a plastic storage bag and submerge it in a bowl of hot tap water for 3–5 minutes.