I have always wondered why some recipes call for pre-sifted flour and other recipes suggest you sift regular all-purpose flour and then why some of these recipes don't turn out well, even when I follow the instructions.
I happened upon this Cooking For Engineers site when trying to figure this out and I found this measuring tip.
When measuring flour without a scale, always assume it calls for sifted flour, because unsifted flour produces different measurements every time. This explains some of the unpredictability of recipes. The author of this site recommends shaking your flour in a large container before measuring. And do NOT pack the flour. It should be lightly spooned in and then leveled off. And shaken in the container first. I've had great results so far!
My favorite containers to store flours, sugars, and other dry goods in are like the Lock and Lock Storage 11 Cup Medium Container.