Making a ruffle is easy! If you're making a self ruffle, cut off the fabric from the skirt and then divide that in half (top half, bottom half) or make it whatever length you want if half is too long--keep in mind you need seam allowances for hemming and gathering the ruffle, and that it will be all frilly and not lie flat so it will appear shorter than it is. Take apart the seams of your ruffle pieces and then sew the pieces together to make one long tube (which should be about the double the width of the skirt). Hem one end of the tube, I love the rolled hem foot for this sort of thing. Zig zag the other end. Using the longest stitch on your machine (probably 4), put in two layers of stitching on the zig zagged edge, 1/4 inch and 1/2 inch from the edge. Pull the top thread of each row of stitching to gather until the tube is the width of the skirt. Pin right sides together and sew, gathered side down (using my mom's icky but memorable mnemonic-type saying: "Always sew with a relaxed bottom"). Then turn down the ruffle and press. If the ruffle doesn't want to lie flat, put in a row of stitching on the skirt about 1/4 inch from the seam with the ruffle, catching the gathered/interior part of the ruffle.