Treat your baking powder with care and it will never let you down!
Baking powder is a very perishable substance. Most baking powders are double acting, meaning they react first to water and then again to heat. Always check the date before purchasing baking powder; buy in small amounts unless you know that you will be using it frequently. Store in a cool, dry place and never dip a wet measuring spoon into the can, as it will react to the moisture.