when i'm strip-piecing, i try to cut my strips along the length of the fabric. since it doesn't stretch along the length, my strips are less likely to ripple. also, once i've cut them apart and start joining sets to each other, the fabric between seams will stretch, which means i can ease when i need to ensure the intersections match up without puckers.
i try to cut all my borders along the length. when i do that and starch them heavily, i don't get ruffles.