I try to select design that can use the extra from using lengthwise of the fabric for borders. Length works better as there is less stretching. However, I don't think it makes much difference in smaller quilts so all my crib quilts get cross grain as it takes less fabric.
If you do piece borders, be sure they are pieced on the diagional. Gives a more continuous view of the border. Unless there is a directional print such as stripe which should be matched.