When storing your tablecloths, it can help to roll them as opposed to folding them to help with harsh creases and wrinkles. When they are on the table, weighing them down with placemats and table decor can also help to prevent them from sliding around and crumpling or creasing when in use.
If they do crease, a quick run-over with an iron or a clothes steamer should help any lines drop out for a sleek look.