I agree - look at pattern closely to see the sizes you will eventually be cutting from the fat quarters. Many newer patterns are written for Fat Quarters, Layer Cakes, Charms, Jelly Rolls, etc. But when you look closely at the pattern it really only requires 10", 5", 2 1/2" squares or rectangles or similar - something you can easily cut yourself from your own stash.
On a current block-of-the-month quilt I'm working on, we start with a fat quarter, but end up only using part of it with lots of fabric / scraps left over.