It is extremely important in both baking and cooking to measure your ingredients accurately and the only way to do that is to use the correct vessel. Using the wrong vessel for measuring can drastically alter the accuracy of the measurement. While cooking can be a little more forgiving, it is essential in baking to be as accurate as possible.
For dry ingredients – ALWAYS measure dry ingredients using DRY measuring cups or spoons. The most accurate method is to lightly spoon the ingredients into the measuring cup and then sweep off the excess with a flat utensil. This will ensure that not too much of the ingredient gets packed down into the cup. The ONLY exception to this method is brown sugar which, unless otherwise noted, is measured by packing it down into the measuring cup.
For wet ingredients – ALWAYS measure liquids using either a glass or plastic WET measuring cup. The most accurate method is to place the vessel on a flat surface then pour in the liquid in until it reaches the desired marking. Check for accuracy by bending down so you’re at eye level.
Please note, the most accurate way to measure ANY ingredient is by using a digital food scale. They are very inexpensive but absolutely invaluable in the kitchen, especially for baking.