Basically, it just involves a lot of increasing. For example, the potato chip scarf
has you cast on the number of stitches you need for your ruffle to be the right length. After you knit your first row, you KFB every stitch on the 2nd row. Then you knit rows 3 & 4 even. How often you do an increase row would depend on how "ruffly" you want it to be.