If I have enough fabric, I like to cut 5" strips. Then, if I have a charm quilt, I can subcut 5" squares, or if I have a jelly roll quilt, I can subcut it to 2 1/2" strips. If I don't have 5", I will cut 2 12" strips.
Shorter pieces, I will cut 5" squares or 2 1/2" squares.