Say you need a cup of shortening for a recipe. Grab a liquid measure that will hold at least two cups. Measure 1 cup of water and set it aside...preferably in another cup. *smarty-pants smile* Dry out your measuring cup, then spoon some shortening into it.
Why dry the cup? So the shortening will stick to the bottom and not float to the surface when you add the water in the next step. Trust me, it's a lot easier to complete this process when the shortening stays on the bottom of the cup.When you have what looks like a cup of shortening, pour in the cup of water. The water should stop at the two-cup mark. If it's below, you need more shortening. If it's above, you need to remove some. When you've got the amount correct, pour out the water (careful not to dump your shortening with it). And now you're done!
Side Note: Never use dry measuring cups for liquid measures or vice versa, because they are not interchangeable. The measurement discrepancy might not matter in some stove-top dishes, but the difference could make or break your baked recipe. Remember, baking is a science experiment in your oven. If you get the measurements off, your experiment might fail.