Are you asking because the fabric you're using has a directional print on it? Or because of the grain?
If it's a plain fabric, I just cut strips from WOF (width of fabric) and then cut them to size as needed in that particular quilt.
If it's because you've got some directional print, then, yeah, you might - might want to fussy cut the strips. It really depends on the visual effect you're trying/want to create.
Do you have a picture of the sashing fabric?