The best way to measure flour is to dip it into the bag or flour canister and use your finger or a knife and level it off for an accurate measurement.  I keep an extra knife and a 1 cup measuring cup in the flour canister so I always have it on hand.  Do not pack flour in the measuring cup. 

It is also a good idea to keep flour in an air tight cannister.  I like to have a large matching set for my flour and sugar, and smaller matching cannisters for powdered sugar and brown sugar in my baking cupboard for easy access and to keep Indian Meal Moth, Flour Beetles, Dermestid Beetles, Grain Beetles, ants and any other pest out of your food containers.  Yuk!  It also helps keep your storage area clean. Putting brown sugar in a cannister also helps prevent it from drying out.