I used to do 2 rows of zig zag stitching over a heavier thread. When you're done sewing - on one end wind the threads back and forth across/around a pin so you don't pull the threads out. Pull the zig zags at the other end and try to even out the gathers as you pull the threads. You could divide the ruffle into 4's and mark with pins. Do the same for whatever you're sewing the ruffle to and mark the pins. When you pull the threads to gather, match the pins on the ruffle and the pins on whatever you're sewing the ruffle to.