First you need enough fabric. 1 yard is not enough.
From a fresh piece of fabric(not the tablecloth you mentioned) fold in half and find your center point. Draw the radius for the waist. At the intersection of th fabric fold and the waist radius, measure out the length you want the skirt. At the center point along the radius measure down to this same length. At this point draw a straight line out to the selvages parralel to the fold. From the other to points that you measured along the fold, draw a straight line down to intersect with the other line you previously drew. These should be perpendicular to the fold. This should give you a square skirt.
This may help envision it...(don't mind the waist radius is off slightly)