I’m compiling the tips I’ve put on other sites here for ease of searching. This is one that I use all the time, especially in home dec applications. My students just love it:
When gathering fabric, rather than using the “double row of long stitches” approach that most patterns and books recommend, I sew over dental floss ( preferably unwaxed) with a very wide zigzag stitch, making sure to center the floss between the stitches. I set the width of the zigzag to 5.5-6 mm and the stitch length to 2.5-3 mm. Once the dental floss is in place, it’s a snap to gather very quickly, and it is very easy to control the fullness of the gathers. I use this technique all the time for home-dec, but it is equally useful for fashion sewing, especially if you are attatching ruffles. I also find that it saves wear and tear on the fabric, because you don’t have to manipulate the gathers with as much force.
Makes me kick myself for buying that Pfaff ruffler!